OptimizeCompareInstr should avoid iterating pass the beginning of the MBB when the 'and' instruction is after the comparison.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114506 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMBaseInstrInfo.cpp

@@ -1455,7 +1455,8 @@ OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpMask,
 
   // Check that CPSR isn't set between the comparison instruction and the one we
   // want to change.
-  MachineBasicBlock::const_iterator I = CmpInstr, E = MI;
+  MachineBasicBlock::const_iterator I = CmpInstr, E = MI,
+    B = MI->getParent()->begin();
   --I;
   for (; I != E; --I) {
     const MachineInstr &Instr = *I;
@@ -1469,6 +1470,10 @@ OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpMask,
       if (MO.getReg() == ARM::CPSR)
         return false;
     }
+
+    if (I == B)
+      // The 'and' is below the comparison instruction.
+      return false;
   }
 
   // Set the "zero" bit in CPSR.

test/CodeGen/ARM/2010-09-21-OptCmpBug.ll

@@ -0,0 +1,84 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-darwin10
+
+declare noalias i8* @malloc(i32) nounwind
+
+define internal void @gl_DrawPixels(i32 %width, i32 %height, i32 %format, i32 %type, i8* %pixels) nounwind {
+entry:
+  br i1 undef, label %bb3.i, label %bb3
+
+bb3.i:                                            ; preds = %entry
+  unreachable
+
+gl_error.exit:                                    ; preds = %bb22
+  ret void
+
+bb3:                                              ; preds = %entry
+  br i1 false, label %bb5, label %bb4
+
+bb4:                                              ; preds = %bb3
+  br label %bb5
+
+bb5:                                              ; preds = %bb4, %bb3
+  br i1 undef, label %bb19, label %bb22
+
+bb19:                                             ; preds = %bb5
+  switch i32 %type, label %bb3.i6.i [
+    i32 5120, label %bb1.i13
+    i32 5121, label %bb1.i13
+    i32 6656, label %bb9.i.i6
+  ]
+
+bb9.i.i6:                                         ; preds = %bb19
+  br label %bb1.i13
+
+bb3.i6.i:                                         ; preds = %bb19
+  unreachable
+
+bb1.i13:                                          ; preds = %bb9.i.i6, %bb19, %bb19
+  br i1 undef, label %bb3.i17, label %bb2.i16
+
+bb2.i16:                                          ; preds = %bb1.i13
+  unreachable
+
+bb3.i17:                                          ; preds = %bb1.i13
+  br i1 undef, label %bb4.i18, label %bb23.i
+
+bb4.i18:                                          ; preds = %bb3.i17
+  %0 = mul nsw i32 %height, %width
+  %1 = and i32 %0, 7
+  %not..i = icmp ne i32 %1, 0
+  %2 = zext i1 %not..i to i32
+  %storemerge2.i = add i32 0, %2
+  %3 = call noalias i8* @malloc(i32 %storemerge2.i) nounwind
+  br i1 undef, label %bb3.i9, label %bb9.i
+
+bb9.i:                                            ; preds = %bb4.i18
+  br i1 undef, label %bb13.i19, label %bb.i24.i
+
+bb13.i19:                                         ; preds = %bb9.i
+  br i1 undef, label %bb14.i20, label %bb15.i
+
+bb14.i20:                                         ; preds = %bb13.i19
+  unreachable
+
+bb15.i:                                           ; preds = %bb13.i19
+  unreachable
+
+bb.i24.i:                                         ; preds = %bb.i24.i, %bb9.i
+  %storemerge1.i21.i = phi i32 [ %4, %bb.i24.i ], [ 0, %bb9.i ]
+  %4 = add i32 %storemerge1.i21.i, 1
+  %exitcond47.i = icmp eq i32 %4, %storemerge2.i
+  br i1 %exitcond47.i, label %bb22, label %bb.i24.i
+
+bb23.i:                                           ; preds = %bb3.i17
+  unreachable
+
+bb3.i9:                                           ; preds = %bb4.i18
+  unreachable
+
+bb22:                                             ; preds = %bb.i24.i, %bb5
+  br i1 undef, label %gl_error.exit, label %bb23
+
+bb23:                                             ; preds = %bb22
+  ret void
+}