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-rw-r--r--lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp103
-rw-r--r--lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h4
-rw-r--r--lib/Transforms/Scalar/SimplifyLibCalls.cpp13
-rw-r--r--test/CodeGen/X86/memcmp.ll76
-rw-r--r--test/Transforms/SimplifyLibCalls/memcmp.ll3
5 files changed, 183 insertions, 16 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index e3c219cd0b..e194003da9 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -17,6 +17,7 @@
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Constants.h"
#include "llvm/CallingConv.h"
#include "llvm/DerivedTypes.h"
@@ -5075,6 +5076,105 @@ void SelectionDAGBuilder::LowerCallTo(CallSite CS, SDValue Callee,
}
}
+/// IsOnlyUsedInZeroEqualityComparison - Return true if it only matters that the
+/// value is equal or not-equal to zero.
+static bool IsOnlyUsedInZeroEqualityComparison(Value *V) {
+ for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
+ UI != E; ++UI) {
+ if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
+ if (IC->isEquality())
+ if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
+ if (C->isNullValue())
+ continue;
+ // Unknown instruction.
+ return false;
+ }
+ return true;
+}
+
+static SDValue getMemCmpLoad(Value *PtrVal, unsigned Size,
+ SelectionDAGBuilder &Builder) {
+ MVT LoadVT;
+ const Type *LoadTy;
+ if (Size == 2) {
+ LoadVT = MVT::i16;
+ LoadTy = Type::getInt16Ty(PtrVal->getContext());
+ } else {
+ LoadVT = MVT::i32;
+ LoadTy = Type::getInt32Ty(PtrVal->getContext());
+ }
+
+ // Check to see if this load can be trivially constant folded, e.g. if the
+ // input is from a string literal.
+ if (Constant *LoadInput = dyn_cast<Constant>(PtrVal)) {
+ // Cast pointer to the type we really want to load.
+ LoadInput = ConstantExpr::getBitCast(LoadInput,
+ PointerType::getUnqual(LoadTy));
+
+ if (Constant *LoadCst = ConstantFoldLoadFromConstPtr(LoadInput, Builder.TD))
+ return Builder.getValue(LoadCst);
+ }
+
+ // Otherwise, we have to emit the load. If the pointer is to unfoldable but
+ // still constant memory, the input chain can be the entry node.
+ SDValue Root;
+ bool ConstantMemory = false;
+
+ // Do not serialize (non-volatile) loads of constant memory with anything.
+ if (Builder.AA->pointsToConstantMemory(PtrVal)) {
+ Root = Builder.DAG.getEntryNode();
+ ConstantMemory = true;
+ } else {
+ // Do not serialize non-volatile loads against each other.
+ Root = Builder.DAG.getRoot();
+ }
+
+ SDValue Ptr = Builder.getValue(PtrVal);
+ SDValue LoadVal = Builder.DAG.getLoad(LoadVT, Builder.getCurDebugLoc(), Root,
+ Ptr, PtrVal /*SrcValue*/, 0/*SVOffset*/,
+ false /*volatile*/, 1 /* align=1 */);
+
+ if (!ConstantMemory)
+ Builder.PendingLoads.push_back(LoadVal.getValue(1));
+ return LoadVal;
+}
+
+
+/// visitMemCmpCall - See if we can lower a call to memcmp in an optimized form.
+/// If so, return true and lower it, otherwise return false and it will be
+/// lowered like a normal call.
+bool SelectionDAGBuilder::visitMemCmpCall(CallInst &I) {
+ // Verify that the prototype makes sense. int memcmp(void*,void*,size_t)
+ if (I.getNumOperands() != 4)
+ return false;
+
+ Value *LHS = I.getOperand(1), *RHS = I.getOperand(2);
+ if (!isa<PointerType>(LHS->getType()) || !isa<PointerType>(RHS->getType()) ||
+ !isa<IntegerType>(I.getOperand(3)->getType()) ||
+ !isa<IntegerType>(I.getType()))
+ return false;
+
+ ConstantInt *Size = dyn_cast<ConstantInt>(I.getOperand(3));
+
+ // memcmp(S1,S2,2) != 0 -> (*(short*)LHS != *(short*)RHS) != 0
+ // memcmp(S1,S2,4) != 0 -> (*(int*)LHS != *(int*)RHS) != 0
+ if (Size && (Size->getValue() == 2 || Size->getValue() == 4) &&
+ IsOnlyUsedInZeroEqualityComparison(&I)) {
+ SDValue LHSVal = getMemCmpLoad(LHS, Size->getZExtValue(), *this);
+ SDValue RHSVal = getMemCmpLoad(RHS, Size->getZExtValue(), *this);
+
+ SDValue Res = DAG.getSetCC(getCurDebugLoc(), MVT::i1, LHSVal, RHSVal,
+ ISD::SETNE);
+ EVT CallVT = TLI.getValueType(I.getType(), true);
+ setValue(&I, DAG.getZExtOrTrunc(Res, getCurDebugLoc(), CallVT));
+ return true;
+ }
+
+
+ return false;
+}
+
+
void SelectionDAGBuilder::visitCall(CallInst &I) {
const char *RenameFn = 0;
if (Function *F = I.getCalledFunction()) {
@@ -5148,6 +5248,9 @@ void SelectionDAGBuilder::visitCall(CallInst &I) {
Tmp.getValueType(), Tmp));
return;
}
+ } else if (Name == "memcmp") {
+ if (visitMemCmpCall(I))
+ return;
}
}
} else if (isa<InlineAsm>(I.getOperand(0))) {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index c9c5f4f87c..88a2017b47 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -91,11 +91,13 @@ class SelectionDAGBuilder {
DenseMap<const Value*, SDValue> NodeMap;
+public:
/// PendingLoads - Loads are not emitted to the program immediately. We bunch
/// them up and then emit token factor nodes when possible. This allows us to
/// get simple disambiguation between loads without worrying about alias
/// analysis.
SmallVector<SDValue, 8> PendingLoads;
+private:
/// PendingExports - CopyToReg nodes that copy values to virtual registers
/// for export to other blocks need to be emitted before any terminator
@@ -461,6 +463,8 @@ private:
void visitStore(StoreInst &I);
void visitPHI(PHINode &I) { } // PHI nodes are handled specially.
void visitCall(CallInst &I);
+ bool visitMemCmpCall(CallInst &I);
+
void visitInlineAsm(CallSite CS);
const char *visitIntrinsicCall(CallInst &I, unsigned Intrinsic);
void visitTargetIntrinsic(CallInst &I, unsigned Intrinsic);
diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index 30c3f3f398..3c28ad27e5 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -1011,19 +1011,6 @@ struct MemCmpOpt : public LibCallOptimization {
return B.CreateSExt(B.CreateSub(LHSV, RHSV, "chardiff"), CI->getType());
}
- // memcmp(S1,S2,2) != 0 -> (*(short*)LHS ^ *(short*)RHS) != 0
- // memcmp(S1,S2,4) != 0 -> (*(int*)LHS ^ *(int*)RHS) != 0
- if ((Len == 2 || Len == 4) && IsOnlyUsedInZeroEqualityComparison(CI)) {
- const Type *PTy = PointerType::getUnqual(Len == 2 ?
- Type::getInt16Ty(*Context) : Type::getInt32Ty(*Context));
- LHS = B.CreateBitCast(LHS, PTy, "tmp");
- RHS = B.CreateBitCast(RHS, PTy, "tmp");
- LoadInst *LHSV = B.CreateLoad(LHS, "lhsv");
- LoadInst *RHSV = B.CreateLoad(RHS, "rhsv");
- LHSV->setAlignment(1); RHSV->setAlignment(1); // Unaligned loads.
- return B.CreateZExt(B.CreateXor(LHSV, RHSV, "shortdiff"), CI->getType());
- }
-
// Constant folding: memcmp(x, y, l) -> cnst (all arguments are constant)
std::string LHSStr, RHSStr;
if (GetConstantStringInfo(LHS, LHSStr) &&
diff --git a/test/CodeGen/X86/memcmp.ll b/test/CodeGen/X86/memcmp.ll
new file mode 100644
index 0000000000..f6086c4fbe
--- /dev/null
+++ b/test/CodeGen/X86/memcmp.ll
@@ -0,0 +1,76 @@
+; RUN: llc %s -o - -march=x86-64 | FileCheck %s
+
+; This tests codegen time inlining/optimization of memcmp
+; rdar://6480398
+
+@.str = private constant [6 x i8] c"fooxx\00", align 1 ; <[6 x i8]*> [#uses=1]
+
+declare i32 @memcmp(...)
+
+define void @memcmp2(i8* %X, i8* %Y, i32* nocapture %P) nounwind {
+entry:
+ %0 = tail call i32 (...)* @memcmp(i8* %X, i8* %Y, i32 2) nounwind ; <i32> [#uses=1]
+ %1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %return, label %bb
+
+bb: ; preds = %entry
+ store i32 4, i32* %P, align 4
+ ret void
+
+return: ; preds = %entry
+ ret void
+; CHECK: memcmp2:
+; CHECK: movw (%rsi), %ax
+; CHECK: cmpw %ax, (%rdi)
+}
+
+define void @memcmp2a(i8* %X, i32* nocapture %P) nounwind {
+entry:
+ %0 = tail call i32 (...)* @memcmp(i8* %X, i8* getelementptr inbounds ([6 x i8]* @.str, i32 0, i32 1), i32 2) nounwind ; <i32> [#uses=1]
+ %1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %return, label %bb
+
+bb: ; preds = %entry
+ store i32 4, i32* %P, align 4
+ ret void
+
+return: ; preds = %entry
+ ret void
+; CHECK: memcmp2a:
+; CHECK: cmpw $28527, (%rdi)
+}
+
+
+define void @memcmp4(i8* %X, i8* %Y, i32* nocapture %P) nounwind {
+entry:
+ %0 = tail call i32 (...)* @memcmp(i8* %X, i8* %Y, i32 4) nounwind ; <i32> [#uses=1]
+ %1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %return, label %bb
+
+bb: ; preds = %entry
+ store i32 4, i32* %P, align 4
+ ret void
+
+return: ; preds = %entry
+ ret void
+; CHECK: memcmp4:
+; CHECK: movl (%rsi), %eax
+; CHECK: cmpl %eax, (%rdi)
+}
+
+define void @memcmp4a(i8* %X, i32* nocapture %P) nounwind {
+entry:
+ %0 = tail call i32 (...)* @memcmp(i8* %X, i8* getelementptr inbounds ([6 x i8]* @.str, i32 0, i32 1), i32 4) nounwind ; <i32> [#uses=1]
+ %1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %return, label %bb
+
+bb: ; preds = %entry
+ store i32 4, i32* %P, align 4
+ ret void
+
+return: ; preds = %entry
+ ret void
+; CHECK: memcmp4a:
+; CHECK: cmpl $2021158767, (%rdi)
+}
+
diff --git a/test/Transforms/SimplifyLibCalls/memcmp.ll b/test/Transforms/SimplifyLibCalls/memcmp.ll
index ed7bcac467..640d232a7f 100644
--- a/test/Transforms/SimplifyLibCalls/memcmp.ll
+++ b/test/Transforms/SimplifyLibCalls/memcmp.ll
@@ -14,9 +14,6 @@ define void @test(i8* %P, i8* %Q, i32 %N, i32* %IP, i1* %BP) {
volatile store i32 %B, i32* %IP
%C = call i32 @memcmp( i8* %P, i8* %Q, i32 1 ) ; <i32> [#uses=1]
volatile store i32 %C, i32* %IP
- %D = call i32 @memcmp( i8* %P, i8* %Q, i32 2 ) ; <i32> [#uses=1]
- %E = icmp eq i32 %D, 0 ; <i1> [#uses=1]
- volatile store i1 %E, i1* %BP
%F = call i32 @memcmp(i8* getelementptr ([4 x i8]* @hel, i32 0, i32 0),
i8* getelementptr ([8 x i8]* @hello_u, i32 0, i32 0),
i32 3)
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-02-27 13:37:29 +0000