8516f54e6a
This is a mostly-target-independent variadic function optimisation and lowering pass. It is only enabled for AMDGPU in this initial commit. The purpose is to make C style variadic functions a zero cost abstraction. They are lowered to equivalent IR which is then amenable to other optimisations. This is inherently slightly target specific but much less so than one might expect - the C varargs interface heavily constrains the ABI design divergence. The pass is primarily tested from webassembly. This is because wasm has a straightforward variadic lowering strategy which coincides exactly with what this pass transforms code into and a struct passing convention with few cases to check. Adding further targets conventions is straightforward and elided from this patch primarily to simplify the review. Implemented in other branches are Linux X86, AMD64, AArch64 and NVPTX. Testing for targets that have existing lowering for va_arg from clang is most efficiently done by checking that clang | opt completely elides the variadic syntax from test cases. The lowering produces a struct for each call site which can be inspected to check the various alignment and indirections are correct. AMDGPU presently has no variadic support other than some ad hoc printf handling. Combined with the pass being inactive on all other targets landing this represents strict increase in capability with zero risk. Testing and refining will continue post commit. In addition to the compiler tests included here, a self contained x64 clang/musl toolchain was constructed using the "lowering" instead of the systemv ABI and used to build various C programs like lua and libxml2.
90 lines
3.8 KiB
LLVM
90 lines
3.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -mtriple=wasm32-unknown-unknown -S --passes=expand-variadics --expand-variadics-override=optimize < %s | FileCheck %s -check-prefixes=CHECK
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; RUN: not --crash opt -mtriple=wasm32-unknown-unknown -S --passes=expand-variadics --expand-variadics-override=lowering < %s 2>&1 | FileCheck %s -check-prefixes=ERROR
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; REQUIRES: webassembly-registered-target
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target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20"
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; ERROR: LLVM ERROR: Cannot lower callbase instruction
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@_ZTIi = external constant ptr
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; Function Attrs: mustprogress
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define hidden void @test0(i32 noundef %x) #0 personality ptr @__gxx_wasm_personality_v0 {
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; CHECK-LABEL: @test0(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: invoke void (...) @may_throw(i32 noundef [[X:%.*]])
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; CHECK-NEXT: to label [[TRY_CONT:%.*]] unwind label [[CATCH_DISPATCH:%.*]]
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; CHECK: catch.dispatch:
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; CHECK-NEXT: [[TMP0:%.*]] = catchswitch within none [label %catch.start] unwind to caller
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; CHECK: catch.start:
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; CHECK-NEXT: [[TMP1:%.*]] = catchpad within [[TMP0]] [ptr @_ZTIi]
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; CHECK-NEXT: [[TMP2:%.*]] = tail call ptr @llvm.wasm.get.exception(token [[TMP1]])
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; CHECK-NEXT: [[TMP3:%.*]] = tail call i32 @llvm.wasm.get.ehselector(token [[TMP1]])
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; CHECK-NEXT: [[TMP4:%.*]] = tail call i32 @llvm.eh.typeid.for.p0(ptr nonnull @_ZTIi)
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; CHECK-NEXT: [[MATCHES:%.*]] = icmp eq i32 [[TMP3]], [[TMP4]]
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; CHECK-NEXT: br i1 [[MATCHES]], label [[CATCH:%.*]], label [[RETHROW:%.*]]
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; CHECK: catch:
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; CHECK-NEXT: [[TMP5:%.*]] = call ptr @__cxa_begin_catch(ptr [[TMP2]]) [ "funclet"(token [[TMP1]]) ]
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; CHECK-NEXT: call void (...) @dont_throw(i32 noundef [[X]]) [ "funclet"(token [[TMP1]]) ]
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; CHECK-NEXT: call void @__cxa_end_catch() [ "funclet"(token [[TMP1]]) ]
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; CHECK-NEXT: catchret from [[TMP1]] to label [[TRY_CONT]]
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; CHECK: rethrow:
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; CHECK-NEXT: call void @llvm.wasm.rethrow() [ "funclet"(token [[TMP1]]) ]
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; CHECK-NEXT: unreachable
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; CHECK: try.cont:
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; CHECK-NEXT: ret void
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;
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entry:
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invoke void (...) @may_throw(i32 noundef %x)
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to label %try.cont unwind label %catch.dispatch
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catch.dispatch: ; preds = %entry
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%0 = catchswitch within none [label %catch.start] unwind to caller
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catch.start: ; preds = %catch.dispatch
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%1 = catchpad within %0 [ptr @_ZTIi]
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%2 = tail call ptr @llvm.wasm.get.exception(token %1)
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%3 = tail call i32 @llvm.wasm.get.ehselector(token %1)
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%4 = tail call i32 @llvm.eh.typeid.for.p0(ptr nonnull @_ZTIi)
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%matches = icmp eq i32 %3, %4
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br i1 %matches, label %catch, label %rethrow
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catch: ; preds = %catch.start
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%5 = call ptr @__cxa_begin_catch(ptr %2) #6 [ "funclet"(token %1) ]
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call void (...) @dont_throw(i32 noundef %x) #6 [ "funclet"(token %1) ]
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call void @__cxa_end_catch() #6 [ "funclet"(token %1) ]
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catchret from %1 to label %try.cont
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rethrow: ; preds = %catch.start
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call void @llvm.wasm.rethrow() #5 [ "funclet"(token %1) ]
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unreachable
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try.cont: ; preds = %entry, %catch
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ret void
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}
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declare void @may_throw(...)
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declare i32 @__gxx_wasm_personality_v0(...)
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; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn
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declare ptr @llvm.wasm.get.exception(token)
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; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn
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declare i32 @llvm.wasm.get.ehselector(token)
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; Function Attrs: nofree nosync nounwind memory(none)
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declare i32 @llvm.eh.typeid.for.p0(ptr)
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declare ptr @__cxa_begin_catch(ptr)
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; Function Attrs: nounwind
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declare void @dont_throw(...)
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declare void @__cxa_end_catch()
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; Function Attrs: noreturn
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declare void @llvm.wasm.rethrow()
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