[PATCH] D40893: [PowerPC] fix a bug in TCO eligibility check
Hiroshi Inoue via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 8 22:52:53 PST 2017
inouehrs updated this revision to Diff 126264.
inouehrs added a comment.
combined with r319218 "[PowerPC] Allow tail calls of fastcc functions from C CallingConv functions."
https://reviews.llvm.org/D40893
Files:
lib/Target/PowerPC/PPCISelLowering.cpp
test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
test/CodeGen/PowerPC/ppc64-sibcall.ll
Index: test/CodeGen/PowerPC/ppc64-sibcall.ll
===================================================================
--- test/CodeGen/PowerPC/ppc64-sibcall.ll
+++ test/CodeGen/PowerPC/ppc64-sibcall.ll
@@ -41,6 +41,15 @@
; CHECK-SCO: b callee_64_64_copy
}
+define internal fastcc void @callee_64_64_copy_fastcc([8 x i64] %a, [8 x i64] %b) #0 { ret void }
+define void @caller_64_64_copy_ccc([8 x i64] %a, [8 x i64] %b) #1 {
+ tail call fastcc void @callee_64_64_copy_fastcc([8 x i64] %a, [8 x i64] %b)
+ ret void
+
+; CHECK-SCO-LABEL: caller_64_64_copy_ccc:
+; CHECK-SCO: bl callee_64_64_copy_fastcc
+}
+
define void @caller_64_64_reorder_copy([8 x i64] %a, [8 x i64] %b) #1 {
tail call void @callee_64_64_copy([8 x i64] %b, [8 x i64] %a)
ret void
Index: test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
===================================================================
--- test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
+++ test/CodeGen/PowerPC/duplicate-returns-for-tailcall.ll
@@ -42,10 +42,10 @@
if.then6: ; preds = %if.end4
%call7 = tail call fastcc signext i32 @call3(i32 signext %a, i32 signext %b, i32 signext %c)
br label %return
-; No duplication here because the calling convention mismatch means we won't tail-call
+; tail calling a fastcc function from a ccc function is supported.
; CHECK_LABEL: if.then13:
-; CHECK: tail call fastcc signext i32 @call3
-; CHECK-NEXT: br
+; CHECK: %[[T2:[a-zA-Z0-9]+]] = tail call fastcc signext i32 @call3
+; CHECK-NEXT: ret i32 %[[T2]]
return: ; preds = %if.end4, %if.then6, %if.then2, %if.then
%retval.0 = phi i32 [ %call, %if.then ], [ %call3, %if.then2 ], [ %call7, %if.then6 ], [ %c, %if.end4 ]
Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -4397,13 +4397,18 @@
static bool
areCallingConvEligibleForTCO_64SVR4(CallingConv::ID CallerCC,
CallingConv::ID CalleeCC) {
- // Tail or Sibling call optimization (TCO/SCO) needs callee and caller to
- // have the same calling convention.
- if (CallerCC != CalleeCC)
+ // tail calls are possible with fastcc and ccc.
+ auto isTailCallableCC = [] (CallingConv::ID CC){
+ return CC == CallingConv::C || CC == CallingConv::Fast;
+ };
+ if (!isTailCallableCC(CallerCC) || !isTailCallableCC(CalleeCC))
return false;
- // Tail or Sibling calls can be done with fastcc/ccc.
- return (CallerCC == CallingConv::Fast || CallerCC == CallingConv::C);
+ // We can safely tail call both fastcc and ccc callees from a c calling
+ // convention caller. If the caller is fastcc, we may have less stack space
+ // then a non-fastcc caller with the same signature so disable tail-calls in
+ // that case.
+ return CallerCC == CallingConv::C || CallerCC == CalleeCC;
}
bool
@@ -4438,6 +4443,12 @@
if (any_of(Outs, [](const ISD::OutputArg& OA) { return OA.Flags.isByVal(); }))
return false;
+ // If callee and caller use different calling conventions, we cannot pass
+ // parameters on stack since offsets for the parameter area may be different.
+ if (Caller->getCallingConv() != CalleeCC &&
+ needStackSlotPassParameters(Subtarget, Outs))
+ return false;
+
// No TCO/SCO on indirect call because Caller have to restore its TOC
if (!isFunctionGlobalAddress(Callee) &&
!isa<ExternalSymbolSDNode>(Callee))
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