[llvm] r236886 - Clear kill flags on all used registers when sinking instructions.

[Pete Cooper]

Author: pete
Date: Fri May  8 12:54:32 2015
New Revision: 236886

URL: http://llvm.org/viewvc/llvm-project?rev=236886&view=rev
Log:
Clear kill flags on all used registers when sinking instructions.

The test here was sinking the AND here to a lower BB:

	%vreg7<def> = ANDWri %vreg8, 0; GPR32common:%vreg7,%vreg8
	TBNZW %vreg8<kill>, 0, <BB#1>; GPR32common:%vreg8

which meant that vreg8 was read after it was killed.

This commit changes the code from clearing kill flags on the AND to clearing flags on all registers used by the AND.

Added:
    llvm/trunk/test/CodeGen/AArch64/machine-sink-kill-flags.ll
Modified:
    llvm/trunk/lib/CodeGen/MachineSink.cpp

Modified: llvm/trunk/lib/CodeGen/MachineSink.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineSink.cpp?rev=236886&r1=236885&r2=236886&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineSink.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineSink.cpp Fri May  8 12:54:32 2015
@@ -756,7 +756,13 @@ bool MachineSinking::SinkInstruction(Mac
 
   // Conservatively, clear any kill flags, since it's possible that they are no
   // longer correct.
-  MI->clearKillInfo();
+  // Note that we have to clear the kill flags for any register this instruction
+  // uses as we may sink over another instruction which currently kills the
+  // used registers.
+  for (MachineOperand &MO : MI->operands()) {
+    if (MO.isReg() && MO.isUse())
+      MRI->clearKillFlags(MO.getReg());
+  }
 
   return true;
 }

Added: llvm/trunk/test/CodeGen/AArch64/machine-sink-kill-flags.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/machine-sink-kill-flags.ll?rev=236886&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/machine-sink-kill-flags.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/machine-sink-kill-flags.ll Fri May  8 12:54:32 2015
@@ -0,0 +1,29 @@
+; RUN: llc %s -o - -fast-isel=true -O1 -verify-machineinstrs | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+target triple = "arm64-apple-ios8.0.0"
+
+; The machine verifier was asserting on this test because the AND instruction was
+; sunk below the test which killed %tmp340.
+; The kill flags on the test had to be cleared because the AND was going to read
+; registers in a BB after the test instruction.
+
+; CHECK: %bb343
+; CHECK: and
+
+define i32 @test(i32* %ptr) {
+bb:
+  br label %.thread
+
+.thread:                                          ; preds = %.thread, %bb
+  %loc = phi i32 [ %next_iter, %.thread ], [ 0, %bb ]
+  %next_iter = lshr i32 %loc, 1
+  %tmp340 = sub i32 %loc, 1
+  %tmp341 = and i32 %tmp340, 1
+  %tmp342 = icmp eq i32 %tmp341, 0
+  br i1 %tmp342, label %bb343, label %.thread
+
+bb343:                                            ; preds = %.thread
+  store i32 %tmp341, i32* %ptr, align 4
+  ret i32 -1
+}