Stackmap shadows should consider call returns a branch target.
To avoid emitting too many nops, a stackmap shadow can include emitted instructions in the shadow, but these must not include branch targets.
A return from a call should count as a branch target as patching over the instructions after the call would lead to incorrect behaviour for threads currently making that call, when they return.
llvm-svn: 220710
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index fc3662e..85cf514 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1210,4 +1210,10 @@
MCInst TmpInst;
MCInstLowering.Lower(MI, TmpInst);
EmitAndCountInstruction(TmpInst);
+
+ // Stackmap shadows cannot include branch targets, so we can count the bytes
+ // in a call towards the shadow, but must flush the shadow immediately after
+ // to account for the return from the call.
+ if (MI->isCall())
+ SMShadowTracker.emitShadowPadding(OutStreamer, getSubtargetInfo());
}