f9d0789064
This PR registers the writeout and reset functions for `gcov` for all modules in the PGO runtime, instead of registering them using global constructors in each module. The change is made for AIX only, but the same mechanism works on Linux on Power. When registering such functions using global constructors in each module without `-ffunction-sections`, the AIX linker cannot garbage collect unused undefined symbols, because such symbols are grouped in the same section as the `__sinit` symbol. Keeping such undefined symbols causes link errors (see test case https://github.com/llvm/llvm-project/pull/108570/files#diff-500a7e1ba871e1b6b61b523700d5e30987900002add306e1b5e4972cf6d5a4f1R1 for this scenario). This PR implements the initialization in the runtime, hence avoiding introducing `__sinit` into each module. The implementation adds a new global variable `__llvm_covinit_functions` to each module. This new global variable contains the function pointers to the `Writeout` and `Reset` functions. `__llvm_covinit_functions`'s section is the named section `__llvm_covinit`. The linker will aggregate all the `__llvm_covinit` sections from each module to form one single named section in the final binary. The pair of functions ``` const __llvm_gcov_init_func_struct *__llvm_profile_begin_covinit(); const __llvm_gcov_init_func_struct *__llvm_profile_end_covinit(); ``` are implemented to return the start and end address of this named section in the final binary, and they are used in function ``` __llvm_profile_gcov_initialize() ``` (which is a constructor function in the runtime) so the runtime knows the addresses of all the `Writeout` and `Reset` functions from all the modules. One noticeable implementation detail relevant to AIX is that to preserve the `__llvm_covinit` from the linker's garbage collection, a `.ref` pseudo instruction is inserted into them, referring to the section that contains the `__llvm_gcov_ctr` variables, which are used in the instrumented code. The `__llvm_gcov_ctr` variables did not belong to named sections before, but this PR added them to the `__llvm_gcov_ctr_section` named section, so we can add a `.ref` pseudo instruction that refers to them in the `__llvm_covinit` section.
139 lines
6.5 KiB
LLVM
139 lines
6.5 KiB
LLVM
; Tests if the __llvm_gcov_ctr section contains a .ref pseudo-op
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; referring to the __llvm_covinit section.
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; RUN: llc < %s | FileCheck --check-prefixes=CHECK,CHECK-RW %s
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; RUN: llc -mxcoff-roptr < %s | FileCheck --check-prefixes=CHECK,CHECK-RO %s
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target datalayout = "E-m:a-p:32:32-Fi32-i64:64-n32"
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target triple = "powerpc-ibm-aix"
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; CHECK-RW: .csect __llvm_covinit[RW],3
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; CHECK-RO: .csect __llvm_covinit[RO],3
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; CHECK-NEXT: .align 3 # @__llvm_covinit_functions
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; CHECK-NEXT: L..__llvm_covinit_functions:
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; CHECK-NEXT: .vbyte 4, __llvm_gcov_writeout[DS]
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; CHECK-NEXT: .vbyte 4, __llvm_gcov_reset[DS]
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; CHECK: .csect __llvm_gcov_ctr_section[RW],3
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; CHECK-NEXT: .lglobl __llvm_gcov_ctr # @_MergedGlobals
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; CHECK-NEXT: .lglobl __llvm_gcov_ctr.1
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; CHECK-NEXT: .align 3
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; CHECK-NEXT: L.._MergedGlobals:
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; CHECK-NEXT: __llvm_gcov_ctr:
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; CHECK-NEXT: .space 16
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; CHECK-NEXT: __llvm_gcov_ctr.1:
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; CHECK-NEXT: .extern .llvm_gcda_start_file[PR]
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; CHECK-NEXT: .extern .llvm_gcda_emit_function[PR]
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; CHECK-NEXT: .extern .llvm_gcda_emit_arcs[PR]
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; CHECK-NEXT: .extern .llvm_gcda_summary_info[PR]
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; CHECK-NEXT: .extern .llvm_gcda_end_file[PR]
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; CHECK-RW-NEXT: .ref __llvm_covinit[RW]
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; CHECK-RO-NEXT: .ref __llvm_covinit[RO]
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%emit_function_args_ty = type { i32, i32, i32 }
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%emit_arcs_args_ty = type { i32, ptr }
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%file_info = type { %start_file_args_ty, i32, ptr, ptr }
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%start_file_args_ty = type { ptr, i32, i32 }
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@__llvm_gcov_ctr = internal global [1 x i64] zeroinitializer, section "__llvm_gcov_ctr_section"
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@__llvm_gcov_ctr.1 = internal global [1 x i64] zeroinitializer, section "__llvm_gcov_ctr_section"
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@0 = private unnamed_addr constant [10 x i8] c"test.gcda\00", align 1
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@__llvm_internal_gcov_emit_function_args.0 = internal unnamed_addr constant [2 x %emit_function_args_ty] [%emit_function_args_ty { i32 0, i32 1961870044, i32 -801444649 }, %emit_function_args_ty { i32 1, i32 1795396728, i32 -801444649 }]
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@__llvm_internal_gcov_emit_arcs_args.0 = internal unnamed_addr constant [2 x %emit_arcs_args_ty] [%emit_arcs_args_ty { i32 1, ptr @__llvm_gcov_ctr }, %emit_arcs_args_ty { i32 1, ptr @__llvm_gcov_ctr.1 }]
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@__llvm_internal_gcov_emit_file_info = internal unnamed_addr constant [1 x %file_info] [%file_info { %start_file_args_ty { ptr @0, i32 875575338, i32 -801444649 }, i32 2, ptr @__llvm_internal_gcov_emit_function_args.0, ptr @__llvm_internal_gcov_emit_arcs_args.0 }]
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@__llvm_covinit_functions = private constant { ptr, ptr } { ptr @__llvm_gcov_writeout, ptr @__llvm_gcov_reset }, section "__llvm_covinit", align 8
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define i32 @bar() {
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entry:
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%gcov_ctr = load i64, ptr @__llvm_gcov_ctr, align 8
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%0 = add i64 %gcov_ctr, 1
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store i64 %0, ptr @__llvm_gcov_ctr, align 8
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ret i32 1
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}
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define i32 @main() {
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entry:
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%gcov_ctr = load i64, ptr @__llvm_gcov_ctr.1, align 8
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%0 = add i64 %gcov_ctr, 1
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store i64 %0, ptr @__llvm_gcov_ctr.1, align 8
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%retval = alloca i32, align 4
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store i32 0, ptr %retval, align 4
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%call = call i32 @bar()
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%sub = sub nsw i32 %call, 1
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ret i32 %sub
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}
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define internal void @__llvm_gcov_writeout() unnamed_addr {
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entry:
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br label %file.loop.header
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file.loop.header: ; preds = %file.loop.latch, %entry
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%file_idx = phi i32 [ 0, %entry ], [ %next_file_idx, %file.loop.latch ]
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%0 = getelementptr inbounds [1 x %file_info], ptr @__llvm_internal_gcov_emit_file_info, i32 0, i32 %file_idx
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%start_file_args = getelementptr inbounds nuw %file_info, ptr %0, i32 0, i32 0
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%1 = getelementptr inbounds nuw %start_file_args_ty, ptr %start_file_args, i32 0, i32 0
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%filename = load ptr, ptr %1, align 4
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%2 = getelementptr inbounds nuw %start_file_args_ty, ptr %start_file_args, i32 0, i32 1
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%version = load i32, ptr %2, align 4
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%3 = getelementptr inbounds nuw %start_file_args_ty, ptr %start_file_args, i32 0, i32 2
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%stamp = load i32, ptr %3, align 4
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call void @llvm_gcda_start_file(ptr %filename, i32 %version, i32 %stamp)
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%4 = getelementptr inbounds nuw %file_info, ptr %0, i32 0, i32 1
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%num_ctrs = load i32, ptr %4, align 4
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%5 = getelementptr inbounds nuw %file_info, ptr %0, i32 0, i32 2
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%emit_function_args = load ptr, ptr %5, align 4
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%6 = getelementptr inbounds nuw %file_info, ptr %0, i32 0, i32 3
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%emit_arcs_args = load ptr, ptr %6, align 4
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%7 = icmp slt i32 0, %num_ctrs
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br i1 %7, label %counter.loop.header, label %file.loop.latch
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counter.loop.header: ; preds = %counter.loop.header, %file.loop.header
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%ctr_idx = phi i32 [ 0, %file.loop.header ], [ %15, %counter.loop.header ]
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%8 = getelementptr inbounds %emit_function_args_ty, ptr %emit_function_args, i32 %ctr_idx
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%9 = getelementptr inbounds nuw %emit_function_args_ty, ptr %8, i32 0, i32 0
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%ident = load i32, ptr %9, align 4
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%10 = getelementptr inbounds nuw %emit_function_args_ty, ptr %8, i32 0, i32 1
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%func_checkssum = load i32, ptr %10, align 4
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%11 = getelementptr inbounds nuw %emit_function_args_ty, ptr %8, i32 0, i32 2
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%cfg_checksum = load i32, ptr %11, align 4
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call void @llvm_gcda_emit_function(i32 %ident, i32 %func_checkssum, i32 %cfg_checksum)
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%12 = getelementptr inbounds %emit_arcs_args_ty, ptr %emit_arcs_args, i32 %ctr_idx
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%13 = getelementptr inbounds nuw %emit_arcs_args_ty, ptr %12, i32 0, i32 0
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%num_counters = load i32, ptr %13, align 4
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%14 = getelementptr inbounds nuw %emit_arcs_args_ty, ptr %12, i32 0, i32 1
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%counters = load ptr, ptr %14, align 4
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call void @llvm_gcda_emit_arcs(i32 %num_counters, ptr %counters)
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%15 = add i32 %ctr_idx, 1
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%16 = icmp slt i32 %15, %num_ctrs
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br i1 %16, label %counter.loop.header, label %file.loop.latch
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file.loop.latch: ; preds = %counter.loop.header, %file.loop.header
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call void @llvm_gcda_summary_info()
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call void @llvm_gcda_end_file()
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%next_file_idx = add i32 %file_idx, 1
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%17 = icmp slt i32 %next_file_idx, 1
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br i1 %17, label %file.loop.header, label %exit
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exit: ; preds = %file.loop.latch
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ret void
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}
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declare void @llvm_gcda_start_file(ptr, i32, i32)
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declare void @llvm_gcda_emit_function(i32, i32, i32)
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declare void @llvm_gcda_emit_arcs(i32, ptr)
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declare void @llvm_gcda_summary_info()
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declare void @llvm_gcda_end_file()
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define internal void @__llvm_gcov_reset() unnamed_addr {
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entry:
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call void @llvm.memset.p0.i64(ptr @__llvm_gcov_ctr, i8 0, i64 8, i1 false)
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call void @llvm.memset.p0.i64(ptr @__llvm_gcov_ctr.1, i8 0, i64 8, i1 false)
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ret void
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}
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declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg)
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