From db8771af286bc84267e7b5bd17eab51cd4ea552f Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 2 Apr 2010 02:21:24 +0000
Subject: [PATCH] After trivial coalescing, the MI being visited may have
 become a copy. Avoid adding it to CSE hash table since copies aren't being
 considered for CSE and they may be deleted. rdar://7819990

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100170 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineCSE.cpp                    |  6 +-
 .../PowerPC/2010-04-01-MachineCSEBug.ll       | 70 +++++++++++++++++++
 2 files changed, 75 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/PowerPC/2010-04-01-MachineCSEBug.ll

diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index fc9dea8e827..597d51d4f37 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -294,8 +294,12 @@ bool MachineCSE::ProcessBlock(MachineDomTreeNode *Node) {
     bool FoundCSE = VNT.count(MI);
     if (!FoundCSE) {
       // Look for trivial copy coalescing opportunities.
-      if (PerformTrivialCoalescing(MI, MBB))
+      if (PerformTrivialCoalescing(MI, MBB)) {
+        // After coalescing MI itself may become a copy.
+        if (isCopy(MI, TII))
+          continue;
         FoundCSE = VNT.count(MI);
+      }
     }
     // FIXME: commute commutable instructions?
 
diff --git a/test/CodeGen/PowerPC/2010-04-01-MachineCSEBug.ll b/test/CodeGen/PowerPC/2010-04-01-MachineCSEBug.ll
new file mode 100644
index 00000000000..8fd05502ba8
--- /dev/null
+++ b/test/CodeGen/PowerPC/2010-04-01-MachineCSEBug.ll
@@ -0,0 +1,70 @@
+; RUN: llc < %s -mtriple=powerpc-apple-darwin10.0
+; rdar://7819990
+
+%0 = type { i32 }
+%1 = type { i64 }
+%struct.Buffer = type { [1024 x i8], i64, i64, i64 }
+%struct.InStream = type { %struct.Buffer, %0, %1, i32*, %struct.InStreamMethods* }
+%struct.InStreamMethods = type { void (%struct.InStream*, i8*, i32)*, void (%struct.InStream*, i64)*, i64 (%struct.InStream*)*, void (%struct.InStream*)* }
+
+define i64 @t(%struct.InStream* %is) nounwind optsize ssp {
+entry:
+  br i1 undef, label %is_read_byte.exit, label %bb.i
+
+bb.i:                                             ; preds = %entry
+  br label %is_read_byte.exit
+
+is_read_byte.exit:                                ; preds = %bb.i, %entry
+  br i1 undef, label %is_read_byte.exit22, label %bb.i21
+
+bb.i21:                                           ; preds = %is_read_byte.exit
+  unreachable
+
+is_read_byte.exit22:                              ; preds = %is_read_byte.exit
+  br i1 undef, label %is_read_byte.exit19, label %bb.i18
+
+bb.i18:                                           ; preds = %is_read_byte.exit22
+  br label %is_read_byte.exit19
+
+is_read_byte.exit19:                              ; preds = %bb.i18, %is_read_byte.exit22
+  br i1 undef, label %is_read_byte.exit16, label %bb.i15
+
+bb.i15:                                           ; preds = %is_read_byte.exit19
+  unreachable
+
+is_read_byte.exit16:                              ; preds = %is_read_byte.exit19
+  %0 = shl i64 undef, 32                          ; <i64> [#uses=1]
+  br i1 undef, label %is_read_byte.exit13, label %bb.i12
+
+bb.i12:                                           ; preds = %is_read_byte.exit16
+  unreachable
+
+is_read_byte.exit13:                              ; preds = %is_read_byte.exit16
+  %1 = shl i64 undef, 24                          ; <i64> [#uses=1]
+  br i1 undef, label %is_read_byte.exit10, label %bb.i9
+
+bb.i9:                                            ; preds = %is_read_byte.exit13
+  unreachable
+
+is_read_byte.exit10:                              ; preds = %is_read_byte.exit13
+  %2 = shl i64 undef, 16                          ; <i64> [#uses=1]
+  br i1 undef, label %is_read_byte.exit7, label %bb.i6
+
+bb.i6:                                            ; preds = %is_read_byte.exit10
+  br label %is_read_byte.exit7
+
+is_read_byte.exit7:                               ; preds = %bb.i6, %is_read_byte.exit10
+  %3 = shl i64 undef, 8                           ; <i64> [#uses=1]
+  br i1 undef, label %is_read_byte.exit4, label %bb.i3
+
+bb.i3:                                            ; preds = %is_read_byte.exit7
+  unreachable
+
+is_read_byte.exit4:                               ; preds = %is_read_byte.exit7
+  %4 = or i64 0, %0                               ; <i64> [#uses=1]
+  %5 = or i64 %4, %1                              ; <i64> [#uses=1]
+  %6 = or i64 %5, %2                              ; <i64> [#uses=1]
+  %7 = or i64 %6, %3                              ; <i64> [#uses=1]
+  %8 = or i64 %7, 0                               ; <i64> [#uses=1]
+  ret i64 %8
+}