diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 14 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/trunc-mask-ext.ll | 23 |
2 files changed, 37 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 170b476..bf287f2 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -8564,6 +8564,20 @@ Instruction *InstCombiner::visitZExt(ZExtInst &CI) { } } + // zext(trunc(t) & C) -> (t & C) if C is a mask. + if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse()) + if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) + if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) { + Value *TI0 = TI->getOperand(0); + if (TI0->getType() == CI.getType()) { + unsigned TO = C->getValue().countTrailingOnes(); + if (APIntOps::isMask(TO, C->getValue())) + return + BinaryOperator::Create(Instruction::And, TI0, + ConstantExpr::getZExt(C, CI.getType())); + } + } + return 0; } diff --git a/test/Transforms/InstCombine/trunc-mask-ext.ll b/test/Transforms/InstCombine/trunc-mask-ext.ll new file mode 100644 index 0000000..1499947 --- /dev/null +++ b/test/Transforms/InstCombine/trunc-mask-ext.ll @@ -0,0 +1,23 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis > %t +; RUN: not grep zext %t +; RUN: not grep sext %t + +; Instcombine should be able to eliminate both ext casts. + +declare void @use(i32) + +define i64 @foo(i64 %a) { + %b = trunc i64 %a to i32 + %c = and i32 %b, 15 + %d = zext i32 %c to i64 + call void @use(i32 %b) + ret i64 %d +} +define i64 @bar(i64 %a) { + %b = trunc i64 %a to i32 + %c = shl i32 %b, 4 + %q = ashr i32 %c, 4 + %d = sext i32 %q to i64 + call void @use(i32 %b) + ret i64 %d +} |