[EVM] Fold signextend(b, signextend(b, x)) -> signextend(b, x)

Implement instCombineIntrinsic in TTI and do the folding.
Doing this early in the pipeline, we give LLVM opportunity
to do more optimizations.

Signed-off-by: Vladimir Radosavljevic <[email protected]>

Author: vladimirradosavljevic

llvm/lib/Target/EVM/EVMTargetTransformInfo.cpp

@@ -12,10 +12,33 @@
 //===----------------------------------------------------------------------===//
 
 #include "EVMTargetTransformInfo.h"
+#include "llvm/IR/IntrinsicsEVM.h"
+#include "llvm/Transforms/InstCombine/InstCombiner.h"
 using namespace llvm;
+using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "evmtti"
 
+static std::optional<Instruction *> instCombineSignExtend(InstCombiner &IC,
+                                                          IntrinsicInst &II) {
+  // Fold signextend(b, signextend(b, x)) -> signextend(b, x)
+  Value *B = nullptr, *X = nullptr;
+  if (match(&II, m_Intrinsic<Intrinsic::evm_signextend>(
+                     m_Value(B), m_Intrinsic<Intrinsic::evm_signextend>(
+                                     m_Deferred(B), m_Value(X)))))
+    return IC.replaceInstUsesWith(II, II.getArgOperand(1));
+
+  return std::nullopt;
+}
+
+std::optional<Instruction *>
+EVMTTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
+  if (II.getIntrinsicID() == Intrinsic::evm_signextend)
+    return instCombineSignExtend(IC, II);
+
+  return std::nullopt;
+}
+
 unsigned EVMTTIImpl::getAssumedAddrSpace(const Value *V) const {
   const auto *LD = dyn_cast<LoadInst>(V);
   if (!LD)

llvm/lib/Target/EVM/EVMTargetTransformInfo.h

@@ -42,6 +42,9 @@ class EVMTTIImpl final : public BasicTTIImplBase<EVMTTIImpl> {
       : BaseT(TM, F.getParent()->getDataLayout()), ST(TM->getSubtargetImpl(F)),
         TLI(ST->getTargetLowering()) {}
 
+  std::optional<Instruction *> instCombineIntrinsic(InstCombiner &IC,
+                                                    IntrinsicInst &II) const;
+
   bool allowsMisalignedMemoryAccesses(LLVMContext &Context, unsigned BitWidth,
                                       unsigned AddressSpace = 0,
                                       Align Alignment = Align(1),

llvm/test/CodeGen/EVM/fold-signextend.ll

@@ -8,8 +8,7 @@ define i256 @test_const(i256 %x) {
 ; CHECK-LABEL: define i256 @test_const(
 ; CHECK-SAME: i256 [[X:%.*]]) {
 ; CHECK-NEXT:    [[SIGNEXT1:%.*]] = call i256 @llvm.evm.signextend(i256 15, i256 [[X]])
-; CHECK-NEXT:    [[SIGNEXT2:%.*]] = call i256 @llvm.evm.signextend(i256 15, i256 [[SIGNEXT1]])
-; CHECK-NEXT:    ret i256 [[SIGNEXT2]]
+; CHECK-NEXT:    ret i256 [[SIGNEXT1]]
 ;
   %signext1 = call i256 @llvm.evm.signextend(i256 15, i256 %x)
   %signext2 = call i256 @llvm.evm.signextend(i256 15, i256 %signext1)
@@ -32,8 +31,7 @@ define i256 @test_var(i256 %b, i256 %x) {
 ; CHECK-LABEL: define i256 @test_var(
 ; CHECK-SAME: i256 [[B:%.*]], i256 [[X:%.*]]) {
 ; CHECK-NEXT:    [[SIGNEXT1:%.*]] = call i256 @llvm.evm.signextend(i256 [[B]], i256 [[X]])
-; CHECK-NEXT:    [[SIGNEXT2:%.*]] = call i256 @llvm.evm.signextend(i256 [[B]], i256 [[SIGNEXT1]])
-; CHECK-NEXT:    ret i256 [[SIGNEXT2]]
+; CHECK-NEXT:    ret i256 [[SIGNEXT1]]
 ;
   %signext1 = call i256 @llvm.evm.signextend(i256 %b, i256 %x)
   %signext2 = call i256 @llvm.evm.signextend(i256 %b, i256 %signext1)