reapply the patch reverted in r116033:
"Reimplement (part of) the or -> add optimization. Matching 'or' into 'add'"
With a critical fix: the add pseudos clobber EFLAGS.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116039 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
index 29ee2bf..662717b 100644
--- a/lib/Target/X86/X86MCInstLower.cpp
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -347,6 +347,7 @@
}
// Handle a few special cases to eliminate operand modifiers.
+ReSimplify:
switch (OutMI.getOpcode()) {
case X86::LEA64_32r: // Handle 'subreg rewriting' for the lea64_32mem operand.
lower_lea64_32mem(&OutMI, 1);
@@ -433,6 +434,13 @@
break;
}
+ // These are pseudo-ops for OR to help with the OR->ADD transformation. We do
+ // this with an ugly goto in case the resultant OR uses EAX and needs the
+ // short form.
+ case X86::ADD16rr_DB: OutMI.setOpcode(X86::OR16rr); goto ReSimplify;
+ case X86::ADD32rr_DB: OutMI.setOpcode(X86::OR32rr); goto ReSimplify;
+ case X86::ADD64rr_DB: OutMI.setOpcode(X86::OR64rr); goto ReSimplify;
+
// The assembler backend wants to see branches in their small form and relax
// them to their large form. The JIT can only handle the large form because
// it does not do relaxation. For now, translate the large form to the