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Minor extension to llvm.experimental.patchpoint: don't require a call.

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If a null call target is provided, don't emit a dummy call. This
allows the runtime to reserve as little nop space as it needs without
the requirement of emitting a call.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194676 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2013-11-14 06:54:10 +00:00
parent 27df434c5e
commit 72cf01cc7c
3 changed files with 33 additions and 12 deletions
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2
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
View File

@ -6826,7 +6826,7 @@ void SelectionDAGBuilder::visitStackmap(const CallInst &CI) {
/// \brief Lower llvm.experimental.patchpoint directly to its target opcode.
void SelectionDAGBuilder::visitPatchpoint(const CallInst &CI) {
// void|i64 @llvm.experimental.patchpoint.void|i64(i32 <id>,
// i32 <numNopBytes>,
// i32 <numBytes>,
// i8* <target>,
// i32 <numArgs>,
// [Args...],

27
lib/Target/X86/X86MCInstLower.cpp
View File

@ -765,6 +765,8 @@ static void LowerSTACKMAP(MCStreamer &OutStreamer,
OutStreamer.EmitInstruction(MCInstBuilder(X86::NOOP));
}
// Lower a patchpoint of the form:
// [<def>], <id>, <numBytes>, <target>, <numArgs>
static void LowerPATCHPOINT(MCStreamer &OutStreamer,
X86MCInstLower &MCInstLowering,
StackMaps &SM,
@ -813,17 +815,20 @@ static void LowerPATCHPOINT(MCStreamer &OutStreamer,
getStackMapEndMOP(MI.operands_begin(), MI.operands_end()),
isAnyRegCC && hasDef);
// Emit MOV to materialize the target address and the CALL to target.
// This is encoded with 12-13 bytes, depending on which register is used.
// We conservatively assume that it is 12 bytes and emit in worst case one
// extra NOP byte.
unsigned EncodedBytes = 12;
OutStreamer.EmitInstruction(MCInstBuilder(X86::MOV64ri)
.addReg(MI.getOperand(ScratchIdx).getReg())
.addImm(MI.getOperand(StartIdx + 2).getImm()));
OutStreamer.EmitInstruction(MCInstBuilder(X86::CALL64r)
.addReg(MI.getOperand(ScratchIdx).getReg()));
unsigned EncodedBytes = 0;
int64_t CallTarget = MI.getOperand(StartIdx + 2).getImm();
if (CallTarget) {
// Emit MOV to materialize the target address and the CALL to target.
// This is encoded with 12-13 bytes, depending on which register is used.
// We conservatively assume that it is 12 bytes and emit in worst case one
// extra NOP byte.
EncodedBytes = 12;
OutStreamer.EmitInstruction(MCInstBuilder(X86::MOV64ri)
.addReg(MI.getOperand(ScratchIdx).getReg())
.addImm(CallTarget));
OutStreamer.EmitInstruction(MCInstBuilder(X86::CALL64r)
.addReg(MI.getOperand(ScratchIdx).getReg()));
}
// Emit padding.
unsigned NumNOPBytes = MI.getOperand(StartIdx + 1).getImm();
assert(NumNOPBytes >= EncodedBytes &&

16
test/CodeGen/X86/patchpoint.ll
View File

@ -79,6 +79,22 @@ entry:
ret i64 10
}
; Test small patchpoints that don't emit calls.
define void @small_patchpoint_codegen(i64 %p1, i64 %p2, i64 %p3, i64 %p4) {
entry:
; CHECK-LABEL: small_patchpoint_codegen:
; CHECK: Ltmp
; CHECK: nop
; CHECK-NEXT: nop
; CHECK-NEXT: nop
; CHECK-NEXT: nop
; CHECK-NEXT: nop
; CHECK-NEXT: popq
; CHECK-NEXT: ret
%result = tail call i64 (i32, i32, i8*, i32, ...)* @llvm.experimental.patchpoint.i64(i32 5, i32 5, i8* null, i32 2, i64 %p1, i64 %p2)
ret void
}
declare void @llvm.experimental.stackmap(i32, i32, ...)
declare void @llvm.experimental.patchpoint.void(i32, i32, i8*, i32, ...)
declare i64 @llvm.experimental.patchpoint.i64(i32, i32, i8*, i32, ...)