From: Pete Cooper <peter_cooper@apple.com>
Date: Thu, 7 May 2015 21:48:26 +0000 (+0000)
Subject: Clear kill flags in tail duplication.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=e4eff4b23195596e3dc6d1ed8d10450557a36c2b;p=oota-llvm.git

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236782 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp
index 04b39922627..23f41c8dd4b 100644
--- a/lib/CodeGen/TailDuplication.cpp
+++ b/lib/CodeGen/TailDuplication.cpp
@@ -449,6 +449,9 @@ void TailDuplicatePass::DuplicateInstruction(MachineInstr *MI,
       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));
       }
     }
diff --git a/test/CodeGen/ARM/tail-dup-kill-flags.ll b/test/CodeGen/ARM/tail-dup-kill-flags.ll
new file mode 100644
index 00000000000..bce6cdc4e28
--- /dev/null
+++ b/test/CodeGen/ARM/tail-dup-kill-flags.ll
@@ -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()