From b3e91f6ae075ca04a8f7862782d595c363496ac7 Mon Sep 17 00:00:00 2001 From: Meador Inge Date: Mon, 12 Nov 2012 14:00:45 +0000 Subject: [PATCH] Normalize memcmp constant folding results. The library call simplifier folds memcmp calls with all constant arguments to a constant. For example: memcmp("foo", "foo", 3) -> 0 memcmp("hel", "foo", 3) -> 1 memcmp("foo", "hel", 3) -> -1 The folding is implemented in terms of the system memcmp that LLVM gets linked with. It currently just blindly uses the value returned from the system memcmp as the folded constant. This patch normalizes the values returned from the system memcmp to (-1, 0, 1) so that we get consistent results across multiple platforms. The test cases were adjusted accordingly. llvm-svn: 167726 --- llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp | 9 ++++++++- llvm/test/Transforms/InstCombine/memcmp-1.ll | 4 ++-- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp index c3ea638..2028118 100644 --- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp @@ -951,7 +951,14 @@ struct MemCmpOpt : public LibCallOptimization { // Make sure we're not reading out-of-bounds memory. if (Len > LHSStr.size() || Len > RHSStr.size()) return 0; - uint64_t Ret = memcmp(LHSStr.data(), RHSStr.data(), Len); + // Fold the memcmp and normalize the result. This way we get consistent + // results across multiple platforms. + uint64_t Ret = 0; + int Cmp = memcmp(LHSStr.data(), RHSStr.data(), Len); + if (Cmp < 0) + Ret = -1; + else if (Cmp > 0) + Ret = 1; return ConstantInt::get(CI->getType(), Ret); } diff --git a/llvm/test/Transforms/InstCombine/memcmp-1.ll b/llvm/test/Transforms/InstCombine/memcmp-1.ll index 4238c5f..c97b201 100644 --- a/llvm/test/Transforms/InstCombine/memcmp-1.ll +++ b/llvm/test/Transforms/InstCombine/memcmp-1.ll @@ -59,7 +59,7 @@ define i32 @test_simplify5() { %mem2 = getelementptr [4 x i8]* @foo, i32 0, i32 0 %ret = call i32 @memcmp(i8* %mem1, i8* %mem2, i32 3) ret i32 %ret -; CHECK: ret i32 {{[0-9]+}} +; CHECK: ret i32 1 } define i32 @test_simplify6() { @@ -68,5 +68,5 @@ define i32 @test_simplify6() { %mem2 = getelementptr [4 x i8]* @hel, i32 0, i32 0 %ret = call i32 @memcmp(i8* %mem1, i8* %mem2, i32 3) ret i32 %ret -; CHECK: ret i32 {{-[0-9]+}} +; CHECK: ret i32 -1 } -- 2.7.4