From 3b671022e4518166fc5a72e88786db037fb7708c Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Thu, 2 Jul 2020 21:35:40 +0200 Subject: [PATCH] [InstSimplify] Simplify comparison between zext(x) and sext(x) This is picking up a loose thread from D69006: We can simplify (zext x) ule (sext x) and (zext x) sge (sext x) to true, with various permutations. Oddly, SCEV knows about this identity, but nothing on the IR level does. Differential Revision: https://reviews.llvm.org/D83081 --- llvm/lib/Analysis/InstructionSimplify.cpp | 18 ++++++++++ llvm/test/Transforms/InstSimplify/cmp_ext.ll | 50 ++++++---------------------- 2 files changed, 28 insertions(+), 40 deletions(-) diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index 817d23a..df4abe0 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3404,6 +3404,15 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, MaxRecurse-1)) return V; } + // Fold (zext X) ule (sext X), (zext X) sge (sext X) to true. + else if (SExtInst *RI = dyn_cast(RHS)) { + if (SrcOp == RI->getOperand(0)) { + if (Pred == ICmpInst::ICMP_ULE || Pred == ICmpInst::ICMP_SGE) + return ConstantInt::getTrue(ITy); + if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SLT) + return ConstantInt::getFalse(ITy); + } + } // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended // too. If not, then try to deduce the result of the comparison. else if (ConstantInt *CI = dyn_cast(RHS)) { @@ -3463,6 +3472,15 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, Q, MaxRecurse-1)) return V; } + // Fold (sext X) uge (zext X), (sext X) sle (zext X) to true. + else if (ZExtInst *RI = dyn_cast(RHS)) { + if (SrcOp == RI->getOperand(0)) { + if (Pred == ICmpInst::ICMP_UGE || Pred == ICmpInst::ICMP_SLE) + return ConstantInt::getTrue(ITy); + if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SGT) + return ConstantInt::getFalse(ITy); + } + } // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended // too. If not, then try to deduce the result of the comparison. else if (ConstantInt *CI = dyn_cast(RHS)) { diff --git a/llvm/test/Transforms/InstSimplify/cmp_ext.ll b/llvm/test/Transforms/InstSimplify/cmp_ext.ll index 4bbe23b..63d3652 100644 --- a/llvm/test/Transforms/InstSimplify/cmp_ext.ll +++ b/llvm/test/Transforms/InstSimplify/cmp_ext.ll @@ -16,10 +16,7 @@ define i1 @zext_uge_sext(i32 %x) { define i1 @zext_ugt_sext(i32 %x) { ; CHECK-LABEL: @zext_ugt_sext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[ZEXT]], [[SEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 false ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -42,10 +39,7 @@ define i1 @zext_ult_sext(i32 %x) { define i1 @zext_ule_sext(i32 %x) { ; CHECK-LABEL: @zext_ule_sext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp ule i64 [[ZEXT]], [[SEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 true ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -55,10 +49,7 @@ define i1 @zext_ule_sext(i32 %x) { define i1 @zext_sge_sext(i32 %x) { ; CHECK-LABEL: @zext_sge_sext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp sge i64 [[ZEXT]], [[SEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 true ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -81,10 +72,7 @@ define i1 @zext_sgt_sext(i32 %x) { define i1 @zext_slt_sext(i32 %x) { ; CHECK-LABEL: @zext_slt_sext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp slt i64 [[ZEXT]], [[SEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 false ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -107,10 +95,7 @@ define i1 @zext_sle_sext(i32 %x) { define i1 @sext_uge_zext(i32 %x) { ; CHECK-LABEL: @sext_uge_zext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp uge i64 [[SEXT]], [[ZEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 true ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -133,10 +118,7 @@ define i1 @sext_ugt_zext(i32 %x) { define i1 @sext_ult_zext(i32 %x) { ; CHECK-LABEL: @sext_ult_zext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp ult i64 [[SEXT]], [[ZEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 false ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -172,10 +154,7 @@ define i1 @sext_sge_zext(i32 %x) { define i1 @sext_sgt_zext(i32 %x) { ; CHECK-LABEL: @sext_sgt_zext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i64 [[SEXT]], [[ZEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 false ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -198,10 +177,7 @@ define i1 @sext_slt_zext(i32 %x) { define i1 @sext_sle_zext(i32 %x) { ; CHECK-LABEL: @sext_sle_zext( -; CHECK-NEXT: [[SEXT:%.*]] = sext i32 [[X:%.*]] to i64 -; CHECK-NEXT: [[ZEXT:%.*]] = zext i32 [[X]] to i64 -; CHECK-NEXT: [[CMP:%.*]] = icmp sle i64 [[SEXT]], [[ZEXT]] -; CHECK-NEXT: ret i1 [[CMP]] +; CHECK-NEXT: ret i1 true ; %sext = sext i32 %x to i64 %zext = zext i32 %x to i64 @@ -211,10 +187,7 @@ define i1 @sext_sle_zext(i32 %x) { define <4 x i1> @zext_ugt_sext_vec(<4 x i32> %x) { ; CHECK-LABEL: @zext_ugt_sext_vec( -; CHECK-NEXT: [[SEXT:%.*]] = sext <4 x i32> [[X:%.*]] to <4 x i64> -; CHECK-NEXT: [[ZEXT:%.*]] = zext <4 x i32> [[X]] to <4 x i64> -; CHECK-NEXT: [[CMP:%.*]] = icmp ugt <4 x i64> [[ZEXT]], [[SEXT]] -; CHECK-NEXT: ret <4 x i1> [[CMP]] +; CHECK-NEXT: ret <4 x i1> zeroinitializer ; %sext = sext <4 x i32> %x to <4 x i64> %zext = zext <4 x i32> %x to <4 x i64> @@ -224,10 +197,7 @@ define <4 x i1> @zext_ugt_sext_vec(<4 x i32> %x) { define <4 x i1> @sext_ult_zext_vec(<4 x i32> %x) { ; CHECK-LABEL: @sext_ult_zext_vec( -; CHECK-NEXT: [[SEXT:%.*]] = sext <4 x i32> [[X:%.*]] to <4 x i64> -; CHECK-NEXT: [[ZEXT:%.*]] = zext <4 x i32> [[X]] to <4 x i64> -; CHECK-NEXT: [[CMP:%.*]] = icmp ult <4 x i64> [[SEXT]], [[ZEXT]] -; CHECK-NEXT: ret <4 x i1> [[CMP]] +; CHECK-NEXT: ret <4 x i1> zeroinitializer ; %sext = sext <4 x i32> %x to <4 x i64> %zext = zext <4 x i32> %x to <4 x i64> -- 2.7.4