From e1b66f11459c7f1523939fb6ac1dfdc93e1d26ef Mon Sep 17 00:00:00 2001 From: Bill Wendling Date: Wed, 29 Feb 2012 01:46:50 +0000 Subject: [PATCH] Restrict this transformation to equality conditions. This transformation is not correct for not-equal conditions: (trunc x) != C1 & (and x, CA) != C2 -> (and x, CA|CMAX) != C1|C2 Let C1 == 0 C2 == 0 CA == 0xFF0000 CMAX == 0xFF and truncating to i8. The original truth table: x | A: trunc x != 0 | B: x & 0xFF0000 != 0 | A & B != 0 -------------------------------------------------------------- 0x00000 | 0 | 0 | 0 0x00001 | 1 | 0 | 0 0x10000 | 0 | 1 | 0 0x10001 | 1 | 1 | 1 The truth table of the replacement: x | x & 0xFF00FF != 0 ---------------------------- 0x00000 | 0 0x00001 | 1 0x10000 | 1 0x10001 | 1 So they are different. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151691 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 7cb56f8fe69..cc8f5bf43e5 100644 --- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -753,7 +753,7 @@ Value *InstCombiner::FoldAndOfICmps(ICmpInst *LHS, ICmpInst *RHS) { // (trunc x) == C1 & (and x, CA) == C2 -> (and x, CA|CMAX) == C1|C2 // where CMAX is the all ones value for the truncated type, // iff the lower bits of C2 and CA are zero. - if (LHSCC == RHSCC && ICmpInst::isEquality(LHSCC) && + if (LHSCC == ICmpInst::ICMP_EQ && LHSCC == RHSCC && LHS->hasOneUse() && RHS->hasOneUse()) { Value *V; ConstantInt *AndCst, *SmallCst = 0, *BigCst = 0; -- 2.34.1