[InstCombine] when calling conventions are compatible, don't convert the call to undef idiom
D24453 enabled libcalls simplication for ARM PCS. This may cause
caller/callee calling conventions mismatch in some situations such as
LTO. This patch makes instcombine aware that the compatible calling
conventions differences are benign (not emitting undef idom).
Differential Revision: https://reviews.llvm.org/D99773
diff --git a/llvm/include/llvm/Analysis/TargetLibraryInfo.h b/llvm/include/llvm/Analysis/TargetLibraryInfo.h
index e913b91..adc6363 100644
--- a/llvm/include/llvm/Analysis/TargetLibraryInfo.h
+++ b/llvm/include/llvm/Analysis/TargetLibraryInfo.h
@@ -192,6 +192,11 @@
/// vector functions.
void getWidestVF(StringRef ScalarF, ElementCount &FixedVF,
ElementCount &Scalable) const;
+
+ /// Returns true if call site / callee has cdecl-compatible calling
+ /// conventions.
+ static bool isCallingConvCCompatible(CallBase *CI);
+ static bool isCallingConvCCompatible(Function *Callee);
};
/// Provides information about what library functions are available for
diff --git a/llvm/lib/Analysis/TargetLibraryInfo.cpp b/llvm/lib/Analysis/TargetLibraryInfo.cpp
index 31cea8f..14dcaa6 100644
--- a/llvm/lib/Analysis/TargetLibraryInfo.cpp
+++ b/llvm/lib/Analysis/TargetLibraryInfo.cpp
@@ -65,6 +65,49 @@
return TT.isOSFreeBSD() || TT.isOSSolaris();
}
+static bool isCallingConvCCompatible(CallingConv::ID CC, Triple TT,
+ FunctionType *FuncTy) {
+ switch (CC) {
+ default:
+ return false;
+ case llvm::CallingConv::C:
+ return true;
+ case llvm::CallingConv::ARM_APCS:
+ case llvm::CallingConv::ARM_AAPCS:
+ case llvm::CallingConv::ARM_AAPCS_VFP: {
+
+ // The iOS ABI diverges from the standard in some cases, so for now don't
+ // try to simplify those calls.
+ if (TT.isiOS())
+ return false;
+
+ if (!FuncTy->getReturnType()->isPointerTy() &&
+ !FuncTy->getReturnType()->isIntegerTy() &&
+ !FuncTy->getReturnType()->isVoidTy())
+ return false;
+
+ for (auto *Param : FuncTy->params()) {
+ if (!Param->isPointerTy() && !Param->isIntegerTy())
+ return false;
+ }
+ return true;
+ }
+ }
+ return false;
+}
+
+bool TargetLibraryInfoImpl::isCallingConvCCompatible(CallBase *CI) {
+ return ::isCallingConvCCompatible(CI->getCallingConv(),
+ Triple(CI->getModule()->getTargetTriple()),
+ CI->getFunctionType());
+}
+
+bool TargetLibraryInfoImpl::isCallingConvCCompatible(Function *F) {
+ return ::isCallingConvCCompatible(F->getCallingConv(),
+ Triple(F->getParent()->getTargetTriple()),
+ F->getFunctionType());
+}
+
/// Initialize the set of available library functions based on the specified
/// target triple. This should be carefully written so that a missing target
/// triple gets a sane set of defaults.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 78f4511..615f10e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2158,9 +2158,14 @@
return &Call;
}
- // If the call and callee calling conventions don't match, this call must
- // be unreachable, as the call is undefined.
- if (CalleeF->getCallingConv() != Call.getCallingConv() &&
+ // If the call and callee calling conventions don't match, and neither one
+ // of the calling conventions is compatible with C calling convention
+ // this call must be unreachable, as the call is undefined.
+ if ((CalleeF->getCallingConv() != Call.getCallingConv() &&
+ !(CalleeF->getCallingConv() == llvm::CallingConv::C &&
+ TargetLibraryInfoImpl::isCallingConvCCompatible(&Call)) &&
+ !(Call.getCallingConv() == llvm::CallingConv::C &&
+ TargetLibraryInfoImpl::isCallingConvCCompatible(CalleeF))) &&
// Only do this for calls to a function with a body. A prototype may
// not actually end up matching the implementation's calling conv for a
// variety of reasons (e.g. it may be written in assembly).
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index c279d18..2e44051 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -56,38 +56,6 @@
Func == LibFunc_llabs || Func == LibFunc_strlen;
}
-static bool isCallingConvCCompatible(CallInst *CI) {
- switch(CI->getCallingConv()) {
- default:
- return false;
- case llvm::CallingConv::C:
- return true;
- case llvm::CallingConv::ARM_APCS:
- case llvm::CallingConv::ARM_AAPCS:
- case llvm::CallingConv::ARM_AAPCS_VFP: {
-
- // The iOS ABI diverges from the standard in some cases, so for now don't
- // try to simplify those calls.
- if (Triple(CI->getModule()->getTargetTriple()).isiOS())
- return false;
-
- auto *FuncTy = CI->getFunctionType();
-
- if (!FuncTy->getReturnType()->isPointerTy() &&
- !FuncTy->getReturnType()->isIntegerTy() &&
- !FuncTy->getReturnType()->isVoidTy())
- return false;
-
- for (auto Param : FuncTy->params()) {
- if (!Param->isPointerTy() && !Param->isIntegerTy())
- return false;
- }
- return true;
- }
- }
- return false;
-}
-
/// Return true if it is only used in equality comparisons with With.
static bool isOnlyUsedInEqualityComparison(Value *V, Value *With) {
for (User *U : V->users()) {
@@ -2862,9 +2830,10 @@
// Check for string/memory library functions.
if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
// Make sure we never change the calling convention.
- assert((ignoreCallingConv(Func) ||
- isCallingConvCCompatible(CI)) &&
- "Optimizing string/memory libcall would change the calling convention");
+ assert(
+ (ignoreCallingConv(Func) ||
+ TargetLibraryInfoImpl::isCallingConvCCompatible(CI)) &&
+ "Optimizing string/memory libcall would change the calling convention");
switch (Func) {
case LibFunc_strcat:
return optimizeStrCat(CI, Builder);
@@ -3048,7 +3017,7 @@
LibFunc Func;
Function *Callee = CI->getCalledFunction();
- bool isCallingConvC = isCallingConvCCompatible(CI);
+ bool IsCallingConvC = TargetLibraryInfoImpl::isCallingConvCCompatible(CI);
SmallVector<OperandBundleDef, 2> OpBundles;
CI->getOperandBundlesAsDefs(OpBundles);
@@ -3066,7 +3035,7 @@
// First, check for intrinsics.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
- if (!isCallingConvC)
+ if (!IsCallingConvC)
return nullptr;
// The FP intrinsics have corresponding constrained versions so we don't
// need to check for the StrictFP attribute here.
@@ -3119,7 +3088,7 @@
// Then check for known library functions.
if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
// We never change the calling convention.
- if (!ignoreCallingConv(Func) && !isCallingConvC)
+ if (!ignoreCallingConv(Func) && !IsCallingConvC)
return nullptr;
if (Value *V = optimizeStringMemoryLibCall(CI, Builder))
return V;
@@ -3503,7 +3472,7 @@
LibFunc Func;
Function *Callee = CI->getCalledFunction();
- bool isCallingConvC = isCallingConvCCompatible(CI);
+ bool IsCallingConvC = TargetLibraryInfoImpl::isCallingConvCCompatible(CI);
SmallVector<OperandBundleDef, 2> OpBundles;
CI->getOperandBundlesAsDefs(OpBundles);
@@ -3517,7 +3486,7 @@
return nullptr;
// We never change the calling convention.
- if (!ignoreCallingConv(Func) && !isCallingConvC)
+ if (!ignoreCallingConv(Func) && !IsCallingConvC)
return nullptr;
switch (Func) {
diff --git a/llvm/test/Transforms/InstCombine/call-callconv-mismatch.ll b/llvm/test/Transforms/InstCombine/call-callconv-mismatch.ll
new file mode 100644
index 0000000..de1110d
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/call-callconv-mismatch.ll
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; Verify that a cdecl-compatible calling convention does not trigger emitting
+; unreachable idom `store i1 true, i1* undef`.
+
+define arm_aapcs_vfpcc i8 @bar(i8* %0) {
+; CHECK-LABEL: @bar(
+; CHECK-NEXT: [[TMP2:%.*]] = load i8, i8* [[TMP0:%.*]], align 1
+; CHECK-NEXT: ret i8 [[TMP2]]
+;
+ %2 = load i8, i8* %0, align 1
+ ret i8 %2
+}
+
+define dso_local arm_aapcs_vfpcc i8 @foo(i8* %0) {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT: [[TMP2:%.*]] = call i8 @bar(i8* [[TMP0:%.*]])
+; CHECK-NEXT: ret i8 [[TMP2]]
+;
+ %2 = call i8 @bar(i8* %0)
+ ret i8 %2
+}
