From 5bf7f88ea28dae0cad4f311cc5ef708b6ce50e8f Mon Sep 17 00:00:00 2001 From: Nick Lewycky Date: Thu, 4 Mar 2010 06:54:10 +0000 Subject: [PATCH] Make the 'icmp pred trunc(ext(X)), CST --> icmp pred X, ext(trunc(CST))' transformation much more careful. Truncating binary '01' to '1' sounds like it's safe until you realize that it switched from positive to negative under a signed interpretation, and that depends on the icmp predicate. Also a few miscellaneous cleanups. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97721 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/VMCore/ConstantFold.cpp | 29 ++++--------------- .../InstCombine/2010-03-03-ExtElim.ll | 18 ++++++++++++ 2 files changed, 23 insertions(+), 24 deletions(-) create mode 100644 test/Transforms/InstCombine/2010-03-03-ExtElim.ll diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp index 47244a0e323..549977c2342 100644 --- a/lib/VMCore/ConstantFold.cpp +++ b/lib/VMCore/ConstantFold.cpp @@ -2070,7 +2070,7 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, if (ConstantExpr *CE2 = dyn_cast(C2)) { Constant *CE2Op0 = CE2->getOperand(0); if (CE2->getOpcode() == Instruction::BitCast && - CE2->getType()->isVectorTy()==CE2Op0->getType()->isVectorTy()) { + CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); return ConstantExpr::getICmp(pred, Inverse, CE2Op0); } @@ -2078,8 +2078,8 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, // If the left hand side is an extension, try eliminating it. if (ConstantExpr *CE1 = dyn_cast(C1)) { - if (CE1->getOpcode() == Instruction::SExt || - CE1->getOpcode() == Instruction::ZExt) { + if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || + (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ Constant *CE1Op0 = CE1->getOperand(0); Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); if (CE1Inverse == CE1Op0) { @@ -2097,27 +2097,8 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, // If C2 is a constant expr and C1 isn't, flip them around and fold the // other way if possible. // Also, if C1 is null and C2 isn't, flip them around. - switch (pred) { - case ICmpInst::ICMP_EQ: - case ICmpInst::ICMP_NE: - // No change of predicate required. - return ConstantExpr::getICmp(pred, C2, C1); - - case ICmpInst::ICMP_ULT: - case ICmpInst::ICMP_SLT: - case ICmpInst::ICMP_UGT: - case ICmpInst::ICMP_SGT: - case ICmpInst::ICMP_ULE: - case ICmpInst::ICMP_SLE: - case ICmpInst::ICMP_UGE: - case ICmpInst::ICMP_SGE: - // Change the predicate as necessary to swap the operands. - pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); - return ConstantExpr::getICmp(pred, C2, C1); - - default: // These predicates cannot be flopped around. - break; - } + pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); + return ConstantExpr::getICmp(pred, C2, C1); } } return 0; diff --git a/test/Transforms/InstCombine/2010-03-03-ExtElim.ll b/test/Transforms/InstCombine/2010-03-03-ExtElim.ll new file mode 100644 index 00000000000..2df12d670ad --- /dev/null +++ b/test/Transforms/InstCombine/2010-03-03-ExtElim.ll @@ -0,0 +1,18 @@ +; RUN: opt -instcombine -S %s | FileCheck %s +; PR6486 + +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32" +target triple = "i386-unknown-linux-gnu" + +@g_92 = common global [2 x i32*] zeroinitializer, align 4 ; <[2 x i32*]*> [#uses=1] +@g_177 = constant i32** bitcast (i8* getelementptr (i8* bitcast ([2 x i32*]* @g_92 to i8*), i64 4) to i32**), align 4 ; [#uses=1] + +define i1 @test() nounwind { +; CHECK: @test + %tmp = load i32*** @g_177 ; [#uses=1] + %cmp = icmp ne i32** null, %tmp ; [#uses=1] + %conv = zext i1 %cmp to i32 ; [#uses=1] + %cmp1 = icmp sle i32 0, %conv ; [#uses=1] + ret i1 %cmp1 +; CHECK: ret i1 true +} -- 2.34.1