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-rw-r--r--llvm/include/llvm/CodeGen/Analysis.h14
-rw-r--r--llvm/lib/CodeGen/Analysis.cpp44
-rw-r--r--llvm/lib/CodeGen/CodeGenPrepare.cpp16
-rw-r--r--llvm/test/CodeGen/X86/tailcall-cgp-dup.ll20
4 files changed, 66 insertions, 28 deletions
diff --git a/llvm/include/llvm/CodeGen/Analysis.h b/llvm/include/llvm/CodeGen/Analysis.h
index 2e4dc49a1e2..f20185c4499 100644
--- a/llvm/include/llvm/CodeGen/Analysis.h
+++ b/llvm/include/llvm/CodeGen/Analysis.h
@@ -105,11 +105,21 @@ ISD::CondCode getICmpCondCode(ICmpInst::Predicate Pred);
/// This function only tests target-independent requirements.
bool isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM);
+/// Test if given that the input instruction is in the tail call position, if
+/// there is an attribute mismatch between the caller and the callee that will
+/// inhibit tail call optimizations.
+/// \p AllowDifferingSizes is an output parameter which, if forming a tail call
+/// is permitted, determines whether it's permitted only if the size of the
+/// caller's and callee's return types match exactly.
+bool attributesPermitTailCall(const Function *F, const Instruction *I,
+ const ReturnInst *Ret,
+ const TargetLoweringBase &TLI,
+ bool *AllowDifferingSizes = nullptr);
+
/// Test if given that the input instruction is in the tail call position if the
/// return type or any attributes of the function will inhibit tail call
/// optimization.
-bool returnTypeIsEligibleForTailCall(const Function *F,
- const Instruction *I,
+bool returnTypeIsEligibleForTailCall(const Function *F, const Instruction *I,
const ReturnInst *Ret,
const TargetLoweringBase &TLI);
diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index ebbcaeb3057..6582d24da82 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -525,19 +525,15 @@ bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
}
-bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
- const Instruction *I,
- const ReturnInst *Ret,
- const TargetLoweringBase &TLI) {
- // If the block ends with a void return or unreachable, it doesn't matter
- // what the call's return type is.
- if (!Ret || Ret->getNumOperands() == 0) return true;
+bool llvm::attributesPermitTailCall(const Function *F, const Instruction *I,
+ const ReturnInst *Ret,
+ const TargetLoweringBase &TLI,
+ bool *AllowDifferingSizes) {
+ // ADS may be null, so don't write to it directly.
+ bool DummyADS;
+ bool &ADS = AllowDifferingSizes ? *AllowDifferingSizes : DummyADS;
+ ADS = true;
- // If the return value is undef, it doesn't matter what the call's
- // return type is.
- if (isa<UndefValue>(Ret->getOperand(0))) return true;
-
- // Make sure the attributes attached to each return are compatible.
AttrBuilder CallerAttrs(F->getAttributes(),
AttributeSet::ReturnIndex);
AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
@@ -548,19 +544,18 @@ bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
- bool AllowDifferingSizes = true;
if (CallerAttrs.contains(Attribute::ZExt)) {
if (!CalleeAttrs.contains(Attribute::ZExt))
return false;
- AllowDifferingSizes = false;
+ ADS = false;
CallerAttrs.removeAttribute(Attribute::ZExt);
CalleeAttrs.removeAttribute(Attribute::ZExt);
} else if (CallerAttrs.contains(Attribute::SExt)) {
if (!CalleeAttrs.contains(Attribute::SExt))
return false;
- AllowDifferingSizes = false;
+ ADS = false;
CallerAttrs.removeAttribute(Attribute::SExt);
CalleeAttrs.removeAttribute(Attribute::SExt);
}
@@ -568,7 +563,24 @@ bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
// If they're still different, there's some facet we don't understand
// (currently only "inreg", but in future who knows). It may be OK but the
// only safe option is to reject the tail call.
- if (CallerAttrs != CalleeAttrs)
+ return CallerAttrs == CalleeAttrs;
+}
+
+bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
+ const Instruction *I,
+ const ReturnInst *Ret,
+ const TargetLoweringBase &TLI) {
+ // If the block ends with a void return or unreachable, it doesn't matter
+ // what the call's return type is.
+ if (!Ret || Ret->getNumOperands() == 0) return true;
+
+ // If the return value is undef, it doesn't matter what the call's
+ // return type is.
+ if (isa<UndefValue>(Ret->getOperand(0))) return true;
+
+ // Make sure the attributes attached to each return are compatible.
+ bool AllowDifferingSizes;
+ if (!attributesPermitTailCall(F, I, Ret, TLI, &AllowDifferingSizes))
return false;
const Value *RetVal = Ret->getOperand(0), *CallVal = I;
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 15600af4d39..3bdf60c172a 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -23,6 +23,7 @@
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/CodeGen/Analysis.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
@@ -1983,14 +1984,6 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB) {
if (PN && PN->getParent() != BB)
return false;
- // It's not safe to eliminate the sign / zero extension of the return value.
- // See llvm::isInTailCallPosition().
- const Function *F = BB->getParent();
- AttributeSet CallerAttrs = F->getAttributes();
- if (CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::ZExt) ||
- CallerAttrs.hasAttribute(AttributeSet::ReturnIndex, Attribute::SExt))
- return false;
-
// Make sure there are no instructions between the PHI and return, or that the
// return is the first instruction in the block.
if (PN) {
@@ -2010,13 +2003,15 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB) {
/// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
/// call.
+ const Function *F = BB->getParent();
SmallVector<CallInst*, 4> TailCalls;
if (PN) {
for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
// Make sure the phi value is indeed produced by the tail call.
if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
- TLI->mayBeEmittedAsTailCall(CI))
+ TLI->mayBeEmittedAsTailCall(CI) &&
+ attributesPermitTailCall(F, CI, RetI, *TLI))
TailCalls.push_back(CI);
}
} else {
@@ -2033,7 +2028,8 @@ bool CodeGenPrepare::dupRetToEnableTailCallOpts(BasicBlock *BB) {
continue;
CallInst *CI = dyn_cast<CallInst>(&*RI);
- if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
+ if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI) &&
+ attributesPermitTailCall(F, CI, RetI, *TLI))
TailCalls.push_back(CI);
}
}
diff --git a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
index a51bc889924..26b43e7fe4d 100644
--- a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
+++ b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
@@ -85,3 +85,23 @@ someThingWithValue.exit: ; preds = %if.else.i, %if.then
%retval.0.i = bitcast i8* %retval.0.in.i to %0*
ret %0* %retval.0.i
}
+
+
+; Correctly handle zext returns.
+declare zeroext i1 @foo_i1()
+
+; CHECK-LABEL: zext_i1
+; CHECK: jmp _foo_i1
+define zeroext i1 @zext_i1(i1 %k) {
+entry:
+ br i1 %k, label %land.end, label %land.rhs
+
+land.rhs: ; preds = %entry
+ %call1 = tail call zeroext i1 @foo_i1()
+ br label %land.end
+
+land.end: ; preds = %entry, %land.rhs
+ %0 = phi i1 [ false, %entry ], [ %call1, %land.rhs ]
+ ret i1 %0
+}
+
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