[X86] Fast-ISel was incorrectly always killing the source of a truncate.
A trunc from i32 to i1 on x86_64 generates an instruction such as
%vreg19<def> = COPY %vreg9:sub_8bit<kill>; GR8:%vreg19 GR32:%vreg9
However, the copy here should only have the kill flag on the 32-bit path, not the 64-bit one.
Otherwise, we are killing the source of the truncate which could be used later in the program.
llvm-svn: 236890
diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index 9d81716..3bf4fb8 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -2185,6 +2185,7 @@
return true;
}
+ bool KillInputReg = false;
if (!Subtarget->is64Bit()) {
// If we're on x86-32; we can't extract an i8 from a general register.
// First issue a copy to GR16_ABCD or GR32_ABCD.
@@ -2194,11 +2195,12 @@
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
TII.get(TargetOpcode::COPY), CopyReg).addReg(InputReg);
InputReg = CopyReg;
+ KillInputReg = true;
}
// Issue an extract_subreg.
unsigned ResultReg = fastEmitInst_extractsubreg(MVT::i8,
- InputReg, /*Kill=*/true,
+ InputReg, KillInputReg,
X86::sub_8bit);
if (!ResultReg)
return false;