9694844d7e
Reland https://github.com/llvm/llvm-project/pull/108985 Extend `LoopIdiomRecognize` to find and replace loops of the form ```c base = str; while (*str) ++str; ``` and transforming the `strlen` loop idiom into the appropriate `strlen` and `wcslen` library call which will give a small performance boost if replaced. ```c str = base + strlen(base) len = str - base ```
67 lines
2.3 KiB
LLVM
67 lines
2.3 KiB
LLVM
; RUN: opt -passes='loop(loop-idiom)' < %s -S | FileCheck %s
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target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; invalid libcall prototype
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declare void @strlen(i32)
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declare void @wcslen(i32)
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define i64 @valid_wcslen32(ptr %src) {
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; CHECK-LABEL: valid_wcslen32
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; CHECK-NOT: call {{.*}} @wcslen
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entry:
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%cmp = icmp eq ptr %src, null
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br i1 %cmp, label %return, label %lor.lhs.false
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lor.lhs.false: ; preds = %entry
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%0 = load i32, ptr %src, align 4
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%cmp1 = icmp eq i32 %0, 0
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br i1 %cmp1, label %return, label %while.cond.preheader
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while.cond.preheader: ; preds = %lor.lhs.false
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br label %while.cond
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while.cond: ; preds = %while.cond.preheader, %while.cond
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%src.pn = phi ptr [ %curr.0, %while.cond ], [ %src, %while.cond.preheader ]
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%curr.0 = getelementptr inbounds i8, ptr %src.pn, i64 4
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%1 = load i32, ptr %curr.0, align 4
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%tobool.not = icmp eq i32 %1, 0
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br i1 %tobool.not, label %while.end, label %while.cond
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while.end: ; preds = %while.cond
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%curr.0.lcssa = phi ptr [ %curr.0, %while.cond ]
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%sub.ptr.lhs.cast = ptrtoint ptr %curr.0.lcssa to i64
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%sub.ptr.rhs.cast = ptrtoint ptr %src to i64
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%sub.ptr.sub = sub i64 %sub.ptr.lhs.cast, %sub.ptr.rhs.cast
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%sub.ptr.div = ashr exact i64 %sub.ptr.sub, 2
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br label %return
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return: ; preds = %entry, %lor.lhs.false, %while.end
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%retval.0 = phi i64 [ %sub.ptr.div, %while.end ], [ 0, %lor.lhs.false ], [ 0, %entry ]
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ret i64 %retval.0
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}
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define i64 @valid_strlen(ptr %str) {
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; CHECK-LABEL: valid_strlen
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; CHECK-NOT: call {{.*}} @strlen
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entry:
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br label %while.cond
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while.cond:
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%str.addr.0 = phi ptr [ %str, %entry ], [ %incdec.ptr, %while.cond ]
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%0 = load i8, ptr %str.addr.0, align 1
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%cmp.not = icmp eq i8 %0, 0
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%incdec.ptr = getelementptr i8, ptr %str.addr.0, i64 1
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br i1 %cmp.not, label %while.end, label %while.cond
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while.end:
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%sub.ptr.lhs.cast = ptrtoint ptr %str.addr.0 to i64
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%sub.ptr.rhs.cast = ptrtoint ptr %str to i64
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%sub.ptr.sub = sub i64 %sub.ptr.lhs.cast, %sub.ptr.rhs.cast
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ret i64 %sub.ptr.sub
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}
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!llvm.module.flags = !{!0}
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!0 = !{i32 1, !"wchar_size", i32 4}
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