From b17cb06c354d0ba235ec5fac56b806f068ef25b4 Mon Sep 17 00:00:00 2001 From: Eli Friedman Date: Thu, 17 Dec 2009 22:42:29 +0000 Subject: [PATCH] Allow instcombine to combine "sext(a) >u const" to "a >u trunc(const)". git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91631 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../Scalar/InstructionCombining.cpp | 22 ++++++------- ...004-11-27-SetCCForCastLargerAndConstant.ll | 32 +++++++++++++++++++ ...2006-10-19-SignedToUnsignedCastAndConst.ll | 12 ------- 3 files changed, 42 insertions(+), 24 deletions(-) delete mode 100644 test/Transforms/InstCombine/2006-10-19-SignedToUnsignedCastAndConst.ll diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 2c73e7ae0fe..2a82e0f2335 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -7299,19 +7299,17 @@ Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { // If the re-extended constant didn't change... if (Res2 == CI) { - // Make sure that sign of the Cmp and the sign of the Cast are the same. - // For example, we might have: - // %A = sext i16 %X to i32 - // %B = icmp ugt i32 %A, 1330 - // It is incorrect to transform this into - // %B = icmp ugt i16 %X, 1330 - // because %A may have negative value. - // - // However, we allow this when the compare is EQ/NE, because they are - // signless. - if (isSignedExt == isSignedCmp || ICI.isEquality()) + // Deal with equality cases early. + if (ICI.isEquality()) return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); - return 0; + + // A signed comparison of sign extended values simplifies into a + // signed comparison. + if (isSignedExt && isSignedCmp) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); + + // The other three cases all fold into an unsigned comparison. + return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1); } // The re-extended constant changed so the constant cannot be represented diff --git a/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll b/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll index 187e2f594d6..6672b6c6d4e 100644 --- a/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll +++ b/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll @@ -33,6 +33,14 @@ define i1 @lt_signed_to_large_negative(i8 %SB) { ; CHECK: ret i1 false } +define i1 @lt_signed_to_small_unsigned(i8 %SB) { + %Y = sext i8 %SB to i32 + %C = icmp ult i32 %Y, 17 + ret i1 %C +; CHECK: %C = icmp ult i8 %SB, 17 +; CHECK: ret i1 %C +} + define i1 @lt_signed_to_small_signed(i8 %SB) { %Y = sext i8 %SB to i32 ; [#uses=1] %C = icmp slt i32 %Y, 17 ; [#uses=1] @@ -77,6 +85,14 @@ define i1 @lt_unsigned_to_small_unsigned(i8 %SB) { ; CHECK: ret i1 %C } +define i1 @lt_unsigned_to_small_signed(i8 %SB) { + %Y = zext i8 %SB to i32 + %C = icmp slt i32 %Y, 17 + ret i1 %C +; CHECK: %C = icmp ult i8 %SB, 17 +; CHECK: ret i1 %C +} + define i1 @lt_unsigned_to_small_negative(i8 %SB) { %Y = zext i8 %SB to i32 ; [#uses=1] %C = icmp slt i32 %Y, -17 ; [#uses=1] @@ -106,6 +122,14 @@ define i1 @gt_signed_to_large_negative(i8 %SB) { ; CHECK: ret i1 true } +define i1 @gt_signed_to_small_unsigned(i8 %SB) { + %Y = sext i8 %SB to i32 + %C = icmp ugt i32 %Y, 17 + ret i1 %C +; CHECK: %C = icmp ugt i8 %SB, 17 +; CHECK: ret i1 %C +} + define i1 @gt_signed_to_small_signed(i8 %SB) { %Y = sext i8 %SB to i32 ; [#uses=1] %C = icmp sgt i32 %Y, 17 ; [#uses=1] @@ -151,6 +175,14 @@ define i1 @gt_unsigned_to_small_unsigned(i8 %SB) { ; CHECK: ret i1 %C } +define i1 @gt_unsigned_to_small_signed(i8 %SB) { + %Y = zext i8 %SB to i32 + %C = icmp sgt i32 %Y, 17 + ret i1 %C +; CHECK: %C = icmp ugt i8 %SB, 17 +; CHECK: ret i1 %C +} + define i1 @gt_unsigned_to_small_negative(i8 %SB) { %Y = zext i8 %SB to i32 ; [#uses=1] %C = icmp sgt i32 %Y, -17 ; [#uses=1] diff --git a/test/Transforms/InstCombine/2006-10-19-SignedToUnsignedCastAndConst.ll b/test/Transforms/InstCombine/2006-10-19-SignedToUnsignedCastAndConst.ll deleted file mode 100644 index 4d1a9ef2165..00000000000 --- a/test/Transforms/InstCombine/2006-10-19-SignedToUnsignedCastAndConst.ll +++ /dev/null @@ -1,12 +0,0 @@ -; This test case is reduced from llvmAsmParser.cpp -; The optimizer should not remove the cast here. -; RUN: opt < %s -instcombine -S | \ -; RUN: grep sext.*i32 - - -define i1 @test(i16 %X) { - %A = sext i16 %X to i32 ; [#uses=1] - %B = icmp ugt i32 %A, 1330 ; [#uses=1] - ret i1 %B -} -