[llvm] r236782 - Clear kill flags in tail duplication.

[Pete Cooper]

Author: pete
Date: Thu May  7 16:48:26 2015
New Revision: 236782

URL: http://llvm.org/viewvc/llvm-project?rev=236782&view=rev
Log:
Clear kill flags in tail duplication.

If we duplicate an instruction then we must also clear kill flags on any uses we rewrite.
Otherwise we might be killing a register which was used in other BBs.

For example, here the entry BB ended up with these instructions, the ADD having been tail duplicated.

	%vreg24<def> = t2ADDri %vreg10<kill>, 1, pred:14, pred:%noreg, opt:%noreg; GPRnopc:%vreg24 rGPR:%vreg10
	%vreg22<def> = COPY %vreg10; GPR:%vreg22 rGPR:%vreg10

	The copy here is inserted after the add and so needs vreg10 to be live.

Added:
    llvm/trunk/test/CodeGen/ARM/tail-dup-kill-flags.ll
Modified:
    llvm/trunk/lib/CodeGen/TailDuplication.cpp

Modified: llvm/trunk/lib/CodeGen/TailDuplication.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TailDuplication.cpp?rev=236782&r1=236781&r2=236782&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TailDuplication.cpp (original)
+++ llvm/trunk/lib/CodeGen/TailDuplication.cpp Thu May  7 16:48:26 2015
@@ -449,6 +449,9 @@ void TailDuplicatePass::DuplicateInstruc
       DenseMap<unsigned, unsigned>::iterator VI = LocalVRMap.find(Reg);
       if (VI != LocalVRMap.end()) {
         MO.setReg(VI->second);
+        // Clear any kill flags from this operand.  The new register could have
+        // uses after this one, so kills are not valid here.
+        MO.setIsKill(false);
         MRI->constrainRegClass(VI->second, MRI->getRegClass(Reg));
       }
     }

Added: llvm/trunk/test/CodeGen/ARM/tail-dup-kill-flags.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/tail-dup-kill-flags.ll?rev=236782&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/ARM/tail-dup-kill-flags.ll (added)
+++ llvm/trunk/test/CodeGen/ARM/tail-dup-kill-flags.ll Thu May  7 16:48:26 2015
@@ -0,0 +1,54 @@
+; RUN: llc %s -o - -fast-isel=true -O1 -verify-machineinstrs | FileCheck %s
+
+target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
+target triple = "thumbv7-apple-ios8.0.0"
+
+; Tail duplication was incorrectly leaving kill flags on the duplicated instructions.
+; The machine verifier is able to spot this error, so this test should pass if it passes verification.
+
+; CHECK-LABEL: @test
+
+%struct.cdiff_ctx = type { i8*, %struct.cdiff_node*, %struct.cdiff_node*, %struct.cdiff_node*, %struct.cdiff_node* }
+%struct.cdiff_node = type { i32, i8*, i8*, %struct.cdiff_node* }
+
+declare i32 @logg(i32)
+
+define hidden i32 @test(%struct.cdiff_ctx* nocapture %ctx, %struct.cdiff_node* %tmp10) {
+bb:
+  br label %.outer
+
+bb33:                                             ; preds = %bb92, %.outer
+  %lines.0 = phi i32 [ %tmp37, %bb92 ], [ %lines.0.ph, %.outer ]
+  %tmp37 = add i32 %lines.0, 1
+  %tmp39 = load i32, i32* %tmp57, align 4
+  %tmp40 = icmp eq i32 %tmp39, %tmp37
+  br i1 %tmp40, label %bb41, label %bb92
+
+bb41:                                             ; preds = %bb33
+  %tmp45 = call i32 @strncmp()
+  %tmp46 = icmp eq i32 %tmp45, 0
+  br i1 %tmp46, label %bb53, label %bb47
+
+bb47:                                             ; preds = %bb41
+  %tmp52 = call i32 @logg(i32 %tmp37)
+  ret i32 -1
+
+bb53:                                             ; preds = %bb41
+  %tmp54 = getelementptr inbounds %struct.cdiff_node, %struct.cdiff_node* %del.0.ph, i32 0, i32 3
+  %tmp55 = load %struct.cdiff_node*, %struct.cdiff_node** %tmp54, align 4
+  br label %.outer
+
+.outer:                                           ; preds = %bb53, %bb
+  %del.0.ph = phi %struct.cdiff_node* [ %tmp55, %bb53 ], [ null, %bb ]
+  %lines.0.ph = phi i32 [ 1, %bb53 ], [ 0, %bb ]
+  %tmp57 = getelementptr inbounds %struct.cdiff_node, %struct.cdiff_node* %del.0.ph, i32 0, i32 0
+  br label %bb33
+
+bb92:                                             ; preds = %bb33
+  %tmp93 = call i32 @puts()
+  br label %bb33
+}
+
+declare i32 @strncmp()
+
+declare i32 @puts()