[llvm-commits] [llvm] r164561 - in /llvm/trunk: lib/Transforms/Scalar/DeadStoreElimination.cpp test/Transforms/DeadStoreElimination/libcalls.ll
Nick Lewycky
nicholas at mxc.ca
Mon Sep 24 15:09:11 PDT 2012
Author: nicholas
Date: Mon Sep 24 17:09:10 2012
New Revision: 164561
URL: http://llvm.org/viewvc/llvm-project?rev=164561&view=rev
Log:
Teach DSE that strcpy, strncpy, strcat and strncat are all stores which may be
dead.
Added:
llvm/trunk/test/Transforms/DeadStoreElimination/libcalls.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=164561&r1=164560&r2=164561&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Mon Sep 24 17:09:10 2012
@@ -30,6 +30,7 @@
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SetVector.h"
@@ -146,7 +147,7 @@
/// hasMemoryWrite - Does this instruction write some memory? This only returns
/// true for things that we can analyze with other helpers below.
-static bool hasMemoryWrite(Instruction *I) {
+static bool hasMemoryWrite(Instruction *I, const TargetLibraryInfo *TLI) {
if (isa<StoreInst>(I))
return true;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
@@ -161,6 +162,26 @@
return true;
}
}
+ if (CallSite CS = I) {
+ if (Function *F = CS.getCalledFunction()) {
+ if (TLI && TLI->has(LibFunc::strcpy) &&
+ F->getName() == TLI->getName(LibFunc::strcpy)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strncpy) &&
+ F->getName() == TLI->getName(LibFunc::strncpy)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strcat) &&
+ F->getName() == TLI->getName(LibFunc::strcat)) {
+ return true;
+ }
+ if (TLI && TLI->has(LibFunc::strncat) &&
+ F->getName() == TLI->getName(LibFunc::strncat)) {
+ return true;
+ }
+ }
+ }
return false;
}
@@ -208,7 +229,8 @@
/// instruction if any.
static AliasAnalysis::Location
getLocForRead(Instruction *Inst, AliasAnalysis &AA) {
- assert(hasMemoryWrite(Inst) && "Unknown instruction case");
+ assert(hasMemoryWrite(Inst, AA.getTargetLibraryInfo()) &&
+ "Unknown instruction case");
// The only instructions that both read and write are the mem transfer
// instructions (memcpy/memmove).
@@ -225,23 +247,29 @@
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->isUnordered();
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
- case Intrinsic::lifetime_end:
- // Never remove dead lifetime_end's, e.g. because it is followed by a
- // free.
- return false;
- case Intrinsic::init_trampoline:
- // Always safe to remove init_trampoline.
- return true;
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: llvm_unreachable("doesn't pass 'hasMemoryWrite' predicate");
+ case Intrinsic::lifetime_end:
+ // Never remove dead lifetime_end's, e.g. because it is followed by a
+ // free.
+ return false;
+ case Intrinsic::init_trampoline:
+ // Always safe to remove init_trampoline.
+ return true;
- case Intrinsic::memset:
- case Intrinsic::memmove:
- case Intrinsic::memcpy:
- // Don't remove volatile memory intrinsics.
- return !cast<MemIntrinsic>(II)->isVolatile();
+ case Intrinsic::memset:
+ case Intrinsic::memmove:
+ case Intrinsic::memcpy:
+ // Don't remove volatile memory intrinsics.
+ return !cast<MemIntrinsic>(II)->isVolatile();
+ }
}
+
+ if (CallSite CS = I) // If we assume hasMemoryWrite(I) is true,
+ return true; // then there's nothing left to check.
+
+ return false;
}
@@ -252,14 +280,19 @@
if (isa<StoreInst>(I))
return false;
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: return false;
- case Intrinsic::memset:
- case Intrinsic::memcpy:
- // Do shorten memory intrinsics.
- return true;
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: return false;
+ case Intrinsic::memset:
+ case Intrinsic::memcpy:
+ // Do shorten memory intrinsics.
+ return true;
+ }
}
+
+ // Don't shorten libcalls calls for now.
+
+ return false;
}
/// getStoredPointerOperand - Return the pointer that is being written to.
@@ -269,12 +302,18 @@
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
return MI->getDest();
- IntrinsicInst *II = cast<IntrinsicInst>(I);
- switch (II->getIntrinsicID()) {
- default: llvm_unreachable("Unexpected intrinsic!");
- case Intrinsic::init_trampoline:
- return II->getArgOperand(0);
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ switch (II->getIntrinsicID()) {
+ default: llvm_unreachable("Unexpected intrinsic!");
+ case Intrinsic::init_trampoline:
+ return II->getArgOperand(0);
+ }
}
+
+ CallSite CS(I);
+ // All the supported functions so far happen to have dest as their first
+ // argument.
+ return CS.getArgument(0);
}
static uint64_t getPointerSize(const Value *V, AliasAnalysis &AA) {
@@ -463,7 +502,7 @@
}
// If we find something that writes memory, get its memory dependence.
- if (!hasMemoryWrite(Inst))
+ if (!hasMemoryWrite(Inst, TLI))
continue;
MemDepResult InstDep = MD->getDependency(Inst);
@@ -630,7 +669,7 @@
MemDepResult Dep = MD->getPointerDependencyFrom(Loc, false, InstPt, BB);
while (Dep.isDef() || Dep.isClobber()) {
Instruction *Dependency = Dep.getInst();
- if (!hasMemoryWrite(Dependency) || !isRemovable(Dependency))
+ if (!hasMemoryWrite(Dependency, TLI) || !isRemovable(Dependency))
break;
Value *DepPointer =
@@ -699,7 +738,7 @@
--BBI;
// If we find a store, check to see if it points into a dead stack value.
- if (hasMemoryWrite(BBI) && isRemovable(BBI)) {
+ if (hasMemoryWrite(BBI, TLI) && isRemovable(BBI)) {
// See through pointer-to-pointer bitcasts
SmallVector<Value *, 4> Pointers;
GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers);
Added: llvm/trunk/test/Transforms/DeadStoreElimination/libcalls.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/libcalls.ll?rev=164561&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/libcalls.ll (added)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/libcalls.ll Mon Sep 24 17:09:10 2012
@@ -0,0 +1,46 @@
+; RUN: opt -S -basicaa -dse < %s | FileCheck %s
+
+declare i8* @strcpy(i8* %dest, i8* %src) nounwind
+define void @test1(i8* %src) {
+; CHECK: @test1
+ %B = alloca [16 x i8]
+ %dest = getelementptr inbounds [16 x i8]* %B, i64 0, i64 0
+; CHECK-NOT: @strcpy
+ %call = call i8* @strcpy(i8* %dest, i8* %src)
+; CHECK: ret void
+ ret void
+}
+
+declare i8* @strncpy(i8* %dest, i8* %src, i32 %n) nounwind
+define void @test2(i8* %src) {
+; CHECK: @test2
+ %B = alloca [16 x i8]
+ %dest = getelementptr inbounds [16 x i8]* %B, i64 0, i64 0
+; CHECK-NOT: @strcpy
+ %call = call i8* @strncpy(i8* %dest, i8* %src, i32 12)
+; CHECK: ret void
+ ret void
+}
+
+declare i8* @strcat(i8* %dest, i8* %src) nounwind
+define void @test3(i8* %src) {
+; CHECK: @test3
+ %B = alloca [16 x i8]
+ %dest = getelementptr inbounds [16 x i8]* %B, i64 0, i64 0
+; CHECK-NOT: @strcpy
+ %call = call i8* @strcat(i8* %dest, i8* %src)
+; CHECK: ret void
+ ret void
+}
+
+declare i8* @strncat(i8* %dest, i8* %src, i32 %n) nounwind
+define void @test4(i8* %src) {
+; CHECK: @test4
+ %B = alloca [16 x i8]
+ %dest = getelementptr inbounds [16 x i8]* %B, i64 0, i64 0
+; CHECK-NOT: @strcpy
+ %call = call i8* @strncat(i8* %dest, i8* %src, i32 12)
+; CHECK: ret void
+ ret void
+}
+
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