[PATCH] D59633: [PowerPC] Look through copies for compare elimination

[Nemanja Ivanovic via Phabricator via llvm-commits]

nemanjai created this revision.
nemanjai added reviewers: hfinkel, jsji, steven.zhang, stefanp.
Herald added subscribers: jdoerfert, kbarton.
Herald added a project: LLVM.

We currently miss the opportunities for optmizing comparisons in the peephole optimizer if the input is the result of a COPY since we look for record-form versions of the producing instruction.

This patch simply lets the optimization peek through copies.


Repository:
  rL LLVM

https://reviews.llvm.org/D59633

Files:
  lib/Target/PowerPC/PPCInstrInfo.cpp
  test/CodeGen/PowerPC/eliminate-compare-of-copy.ll


Index: test/CodeGen/PowerPC/eliminate-compare-of-copy.ll
===================================================================
--- test/CodeGen/PowerPC/eliminate-compare-of-copy.ll
+++ test/CodeGen/PowerPC/eliminate-compare-of-copy.ll
@@ -0,0 +1,28 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN:   -mcpu=pwr8 -ppc-asm-full-reg-names < %s | FileCheck %s
+
+define dso_local signext i32 @func(i32 zeroext %x, i32 zeroext %y) local_unnamed_addr #0 {
+; CHECK-LABEL: func
+; CHECK: or. {{r[0-9]+}}, r4, r3
+; CHECK-NOT: cmplwi
+entry:
+  %or = or i32 %y, %x
+  %tobool = icmp eq i32 %or, 0
+  br i1 %tobool, label %if.else, label %if.then
+
+if.then:                                          ; preds = %entry
+  %call = tail call signext i32 bitcast (i32 (...)* @f1 to i32 ()*)() #2
+  br label %return
+
+if.else:                                          ; preds = %entry
+  %call1 = tail call signext i32 bitcast (i32 (...)* @f2 to i32 ()*)() #2
+  br label %return
+
+return:                                           ; preds = %if.else, %if.then
+  %retval.0 = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
+  ret i32 %retval.0
+}
+
+declare signext i32 @f1(...) local_unnamed_addr #1
+
+declare signext i32 @f2(...) local_unnamed_addr #1
Index: lib/Target/PowerPC/PPCInstrInfo.cpp
===================================================================
--- lib/Target/PowerPC/PPCInstrInfo.cpp
+++ lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -1651,6 +1651,7 @@
   if (OpC == PPC::FCMPUS || OpC == PPC::FCMPUD)
     return false;
 
+  const TargetRegisterInfo *TRI = &getRegisterInfo();
   // The record forms set the condition register based on a signed comparison
   // with zero (so says the ISA manual). This is not as straightforward as it
   // seems, however, because this is always a 64-bit comparison on PPC64, even
@@ -1665,6 +1666,7 @@
   bool is64BitUnsignedCompare = OpC == PPC::CMPLDI || OpC == PPC::CMPLD;
 
   // Get the unique definition of SrcReg.
+  SrcReg = TRI->lookThruCopyLike(SrcReg, MRI);
   MachineInstr *MI = MRI->getUniqueVRegDef(SrcReg);
   if (!MI) return false;
 
@@ -1792,7 +1794,6 @@
   }
 
   // Search for Sub.
-  const TargetRegisterInfo *TRI = &getRegisterInfo();
   --I;
 
   // Get ready to iterate backward from CmpInstr.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D59633.191650.patch
Type: text/x-patch
Size: 2293 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190321/2bde3c1a/attachment.bin>