[llvm] 3abe7ac - [CodeGen] Enable tail call position check for speculatable functions
Victor Huang via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 3 08:53:26 PDT 2020
Author: Victor Huang
Date: 2020-06-03T10:37:45-05:00
New Revision: 3abe7aca455b9a8b9b0f1e1efdaffb50193516dd
URL: https://github.com/llvm/llvm-project/commit/3abe7aca455b9a8b9b0f1e1efdaffb50193516dd
DIFF: https://github.com/llvm/llvm-project/commit/3abe7aca455b9a8b9b0f1e1efdaffb50193516dd.diff
LOG: [CodeGen] Enable tail call position check for speculatable functions
In the function "Analysis.cpp:isInTailCallPosition", it only checks whether
a call is in a tail call position if the call has side effects, access memory
or it is not safe to speculative execute. Therefore, a speculatable function
will not go through tail call position check and improperly tail called when
it is not in a tail-call position. This patch enables tail call position check
for speculatable functions.
Differential Revision: https://reviews.llvm.org/D80661
Added:
llvm/test/CodeGen/PowerPC/tailcall-speculatable-callee.ll
Modified:
llvm/lib/CodeGen/Analysis.cpp
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/Analysis.cpp b/llvm/lib/CodeGen/Analysis.cpp
index c7aafb0bd70a..7da28ffec85c 100644
--- a/llvm/lib/CodeGen/Analysis.cpp
+++ b/llvm/lib/CodeGen/Analysis.cpp
@@ -530,24 +530,23 @@ bool llvm::isInTailCallPosition(const CallBase &Call, const TargetMachine &TM) {
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
- if (Call.mayHaveSideEffects() || Call.mayReadFromMemory() ||
- !isSafeToSpeculativelyExecute(&Call))
- for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
- if (&*BBI == &Call)
- break;
- // Debug info intrinsics do not get in the way of tail call optimization.
- if (isa<DbgInfoIntrinsic>(BBI))
+ // Check for all calls including speculatable functions.
+ for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
+ if (&*BBI == &Call)
+ break;
+ // Debug info intrinsics do not get in the way of tail call optimization.
+ if (isa<DbgInfoIntrinsic>(BBI))
+ continue;
+ // A lifetime end or assume intrinsic should not stop tail call
+ // optimization.
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
+ if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
+ II->getIntrinsicID() == Intrinsic::assume)
continue;
- // A lifetime end or assume intrinsic should not stop tail call
- // optimization.
- if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
- if (II->getIntrinsicID() == Intrinsic::lifetime_end ||
- II->getIntrinsicID() == Intrinsic::assume)
- continue;
- if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
- !isSafeToSpeculativelyExecute(&*BBI))
- return false;
- }
+ if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
+ !isSafeToSpeculativelyExecute(&*BBI))
+ return false;
+ }
const Function *F = ExitBB->getParent();
return returnTypeIsEligibleForTailCall(
diff --git a/llvm/test/CodeGen/PowerPC/tailcall-speculatable-callee.ll b/llvm/test/CodeGen/PowerPC/tailcall-speculatable-callee.ll
new file mode 100644
index 000000000000..9223c27d50aa
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/tailcall-speculatable-callee.ll
@@ -0,0 +1,96 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN: -ppc-asm-full-reg-names -ppc-vsr-nums-as-vr < %s | FileCheck %s
+
+; The tests check the behavior of the tail call decision when the callee is speculatable.
+
+; Callee should be tail called in this function since it is at a tail call position.
+define dso_local double @speculatable_callee_return_use_only (double* nocapture %res, double %a) #0 {
+; CHECK-LABEL: speculatable_callee_return_use_only:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: b callee
+entry:
+ %value = tail call double @callee(double %a) #2
+ ret double %value
+}
+
+; Callee should not be tail called since it is not at a tail call position.
+define dso_local void @speculatable_callee_non_return_use_only (double* nocapture %res, double %a) #0 {
+; CHECK-LABEL: speculatable_callee_non_return_use_only:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: mflr r0
+; CHECK-NEXT: std r30, -16(r1) # 8-byte Folded Spill
+; CHECK-NEXT: std r0, 16(r1)
+; CHECK-NEXT: stdu r1, -48(r1)
+; CHECK-NEXT: mr r30, r3
+; CHECK-NEXT: bl callee
+; CHECK-NEXT: stfdx f1, 0, r30
+; CHECK-NEXT: addi r1, r1, 48
+; CHECK-NEXT: ld r0, 16(r1)
+; CHECK-NEXT: ld r30, -16(r1) # 8-byte Folded Reload
+; CHECK-NEXT: mtlr r0
+; CHECK-NEXT: blr
+entry:
+ %call = tail call double @callee(double %a) #2
+ store double %call, double* %res, align 8
+ ret void
+}
+
+; Callee should not be tail called since it is not at a tail call position.
+define dso_local double @speculatable_callee_multi_use (double* nocapture %res, double %a) #0 {
+ ; CHECK-LABEL: speculatable_callee_multi_use:
+ ; CHECK: # %bb.0: # %entry
+ ; CHECK-NEXT: mflr r0
+ ; CHECK-NEXT: std r30, -16(r1) # 8-byte Folded Spill
+ ; CHECK-NEXT: std r0, 16(r1)
+ ; CHECK-NEXT: stdu r1, -48(r1)
+ ; CHECK-NEXT: mr r30, r3
+ ; CHECK-NEXT: bl callee
+ ; CHECK-NEXT: stfdx f1, 0, r30
+ ; CHECK-NEXT: addi r1, r1, 48
+ ; CHECK-NEXT: ld r0, 16(r1)
+ ; CHECK-NEXT: ld r30, -16(r1) # 8-byte Folded Reload
+ ; CHECK-NEXT: mtlr r0
+ ; CHECK-NEXT: blr
+ entry:
+ %call = tail call double @callee(double %a) #2
+ store double %call, double* %res, align 8
+ ret double %call
+}
+
+; Callee should not be tail called since it is not at a tail call position.
+; FIXME: A speculatable callee can be tail called if it is moved into a valid tail call position.
+define dso_local double @speculatable_callee_intermediate_instructions (double* nocapture %res, double %a) #0 {
+ ; CHECK-LABEL: speculatable_callee_intermediate_instructions:
+ ; CHECK: # %bb.0: # %entry
+ ; CHECK-NEXT: mflr r0
+ ; CHECK-NEXT: std r30, -16(r1) # 8-byte Folded Spill
+ ; CHECK-NEXT: std r0, 16(r1)
+ ; CHECK-NEXT: stdu r1, -48(r1)
+ ; CHECK-NEXT: mr r30, r3
+ ; CHECK-NEXT: bl callee
+ ; CHECK-NEXT: lis r3, 16404
+ ; CHECK-NEXT: ori r3, r3, 52428
+ ; CHECK-NEXT: sldi r3, r3, 32
+ ; CHECK-NEXT: oris r3, r3, 52428
+ ; CHECK-NEXT: ori r3, r3, 52429
+ ; CHECK-NEXT: std r3, 0(r30)
+ ; CHECK-NEXT: addi r1, r1, 48
+ ; CHECK-NEXT: ld r0, 16(r1)
+ ; CHECK-NEXT: ld r30, -16(r1) # 8-byte Folded Reload
+ ; CHECK-NEXT: mtlr r0
+ ; CHECK-NEXT: blr
+
+ entry:
+ %call = tail call double @callee(double %a) #2
+ store double 5.2, double* %res, align 8
+ ret double %call
+}
+
+
+define double @callee(double) #1 {
+ ret double 4.5
+}
+
+attributes #0 = { nounwind }
+attributes #1 = { readnone speculatable }
+attributes #2 = { nounwind noinline }
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