From: Sasa Stankovic <Sasa.Stankovic@imgtec.com>
Date: Thu, 5 Jun 2014 13:42:48 +0000 (+0000)
Subject: Prevent hoisting the instruction whose def might be clobbered by the terminator.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=44215458bd5298d9426373fc07d6492dc3d4d8cd;p=oota-llvm.git

Prevent hoisting the instruction whose def might be clobbered by the terminator.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210261 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index f623a48cf0d..7503e575199 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -1505,10 +1505,17 @@ MachineBasicBlock::iterator findHoistingInsertPosAndDeps(MachineBasicBlock *MBB,
     if (MO.isUse()) {
       for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
         Uses.insert(*AI);
-    } else if (!MO.isDead())
-      // Don't try to hoist code in the rare case the terminator defines a
-      // register that is later used.
-      return MBB->end();
+    } else {
+      if (!MO.isDead())
+        // Don't try to hoist code in the rare case the terminator defines a
+        // register that is later used.
+        return MBB->end();
+
+      // If the terminator defines a register, make sure we don't hoist
+      // the instruction whose def might be clobbered by the terminator.
+      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
+        Defs.insert(*AI);
+    }
   }
 
   if (Uses.empty())
diff --git a/test/CodeGen/Mips/prevent-hoisting.ll b/test/CodeGen/Mips/prevent-hoisting.ll
new file mode 100644
index 00000000000..da665c21090
--- /dev/null
+++ b/test/CodeGen/Mips/prevent-hoisting.ll
@@ -0,0 +1,144 @@
+; RUN: llc -march=mipsel -O3 < %s | FileCheck %s
+
+
+; MIPS direct branches implicitly define register $at. This test makes sure that
+; code hoisting optimization (which moves identical instructions at the start of
+; two basic blocks to the common predecessor block) takes this into account and
+; doesn't move definition of $at to the predecessor block (which would make $at
+; live-in at the start of successor block).
+
+
+; CHECK-LABEL: readLumaCoeff8x8_CABAC
+
+; The check for "addiu" instruction is added so that we can match the correct "b" instruction.
+; CHECK:           addiu ${{[0-9]+}}, $zero, -1
+; CHECK:           b $[[BB0:BB[0-9_]+]]
+
+; Check that sll instruction that writes to $1 starts basic block.
+; CHECK:       {{BB[0-9_#]+}}: 
+; CHECK-NEXT:      sll $1, $[[R0:[0-9]+]], 4
+
+; Check that identical sll instruction starts another basic block.
+; CHECK:       [[BB0]]:
+; CHECK-NEXT:      sll $1, $[[R0]], 4
+
+
+%struct.img_par = type { i32, i32, i32, i32, i32*, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, [16 x [16 x i16]], [6 x [32 x i32]], [16 x [16 x i32]], [4 x [12 x [4 x [4 x i32]]]], [16 x i32], i8**, i32*, i32***, i32**, i32, i32, i32, i32, %struct.Slice*, %struct.macroblock*, i32, i32, i32, i32, i32, i32, %struct.DecRefPicMarking_s*, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, [3 x i32], i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32***, i32***, i32****, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, [3 x [2 x i32]], [3 x [2 x i32]], i32, i32, i32, i32, %struct.timeb, %struct.timeb, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 }
+%struct.Slice = type { i32, i32, i32, i32, i32, i32, i32, i32, i32, %struct.datapartition*, %struct.MotionInfoContexts*, %struct.TextureInfoContexts*, i32, i32*, i32*, i32*, i32, i32*, i32*, i32*, i32 (%struct.img_par*, %struct.inp_par*)*, i32, i32, i32, i32 }
+%struct.datapartition = type { %struct.Bitstream*, %struct.DecodingEnvironment, i32 (%struct.syntaxelement*, %struct.img_par*, %struct.datapartition*)* }
+%struct.Bitstream = type { i32, i32, i32, i32, i8*, i32 }
+%struct.DecodingEnvironment = type { i32, i32, i32, i32, i32, i8*, i32* }
+%struct.syntaxelement = type { i32, i32, i32, i32, i32, i32, i32, i32, void (i32, i32, i32*, i32*)*, void (%struct.syntaxelement*, %struct.img_par*, %struct.DecodingEnvironment*)* }
+%struct.MotionInfoContexts = type { [4 x [11 x %struct.BiContextType]], [2 x [9 x %struct.BiContextType]], [2 x [10 x %struct.BiContextType]], [2 x [6 x %struct.BiContextType]], [4 x %struct.BiContextType], [4 x %struct.BiContextType], [3 x %struct.BiContextType] }
+%struct.BiContextType = type { i16, i8 }
+%struct.TextureInfoContexts = type { [2 x %struct.BiContextType], [4 x %struct.BiContextType], [3 x [4 x %struct.BiContextType]], [10 x [4 x %struct.BiContextType]], [10 x [15 x %struct.BiContextType]], [10 x [15 x %struct.BiContextType]], [10 x [5 x %struct.BiContextType]], [10 x [5 x %struct.BiContextType]], [10 x [15 x %struct.BiContextType]], [10 x [15 x %struct.BiContextType]] }
+%struct.inp_par = type { [1000 x i8], [1000 x i8], [1000 x i8], i32, i32, i32, i32, i32, i32, i32, i32 }
+%struct.macroblock = type { i32, [2 x i32], i32, i32, %struct.macroblock*, %struct.macroblock*, i32, [2 x [4 x [4 x [2 x i32]]]], i32, i64, i64, i32, i32, [4 x i8], [4 x i8], i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32 }
+%struct.DecRefPicMarking_s = type { i32, i32, i32, i32, i32, %struct.DecRefPicMarking_s* }
+%struct.timeb = type { i32, i16, i16, i16 }
+
+@assignSE2partition = external global [0 x [20 x i32]]
+@FIELD_SCAN8x8 = external constant [64 x [2 x i8]]
+
+
+define void @readLumaCoeff8x8_CABAC(%struct.img_par* %img, i32 %b8) {
+
+  %1 = load i32* undef, align 4
+  br i1 false, label %2, label %3
+
+; <label>:2                                       ; preds = %0
+  br label %3
+
+; <label>:3                                       ; preds = %2, %0
+  br i1 undef, label %switch.lookup, label %4
+
+switch.lookup:                                    ; preds = %3
+  br label %4
+
+; <label>:4                                       ; preds = %switch.lookup, %3
+  br i1 undef, label %5, label %6
+
+; <label>:5                                       ; preds = %4
+  br label %6
+
+; <label>:6                                       ; preds = %5, %4
+  %7 = phi [2 x i8]* [ getelementptr inbounds ([64 x [2 x i8]]* @FIELD_SCAN8x8, i32 0, i32 0), %4 ], [ null, %5 ]
+  br i1 undef, label %switch.lookup6, label %8
+
+switch.lookup6:                                   ; preds = %6
+  br label %8
+
+; <label>:8                                       ; preds = %switch.lookup6, %6
+  br i1 undef, label %.loopexit, label %9
+
+; <label>:9                                       ; preds = %8
+  %10 = and i32 %b8, 1
+  %11 = shl nuw nsw i32 %10, 3
+  %12 = getelementptr inbounds %struct.Slice* null, i32 0, i32 9
+  br i1 undef, label %.preheader, label %.preheader11
+
+.preheader11:                                     ; preds = %21, %9
+  %k.014 = phi i32 [ %27, %21 ], [ 0, %9 ]
+  %coef_ctr.013 = phi i32 [ %23, %21 ], [ -1, %9 ]
+  br i1 false, label %13, label %14
+
+; <label>:13                                      ; preds = %.preheader11
+  br label %15
+
+; <label>:14                                      ; preds = %.preheader11
+  br label %15
+
+; <label>:15                                      ; preds = %14, %13
+  %16 = getelementptr inbounds [0 x [20 x i32]]* @assignSE2partition, i32 0, i32 %1, i32 undef
+  %17 = load i32* %16, align 4
+  %18 = getelementptr inbounds %struct.datapartition* null, i32 %17, i32 2
+  %19 = load i32 (%struct.syntaxelement*, %struct.img_par*, %struct.datapartition*)** %18, align 4
+  %20 = call i32 %19(%struct.syntaxelement* undef, %struct.img_par* %img, %struct.datapartition* undef)
+  br i1 false, label %.loopexit, label %21
+
+; <label>:21                                      ; preds = %15
+  %22 = add i32 %coef_ctr.013, 1
+  %23 = add i32 %22, 0
+  %24 = getelementptr inbounds [2 x i8]* %7, i32 %23, i32 0
+  %25 = add nsw i32 0, %11
+  %26 = getelementptr inbounds %struct.img_par* %img, i32 0, i32 27, i32 undef, i32 %25
+  store i32 0, i32* %26, align 4
+  %27 = add nsw i32 %k.014, 1
+  %28 = icmp slt i32 %27, 65
+  br i1 %28, label %.preheader11, label %.loopexit
+
+.preheader:                                       ; preds = %36, %9
+  %k.110 = phi i32 [ %45, %36 ], [ 0, %9 ]
+  %coef_ctr.29 = phi i32 [ %39, %36 ], [ -1, %9 ]
+  br i1 false, label %29, label %30
+
+; <label>:29                                      ; preds = %.preheader
+  br label %31
+
+; <label>:30                                      ; preds = %.preheader
+  br label %31
+
+; <label>:31                                      ; preds = %30, %29
+  %32 = getelementptr inbounds [0 x [20 x i32]]* @assignSE2partition, i32 0, i32 %1, i32 undef
+  %33 = load i32* %32, align 4
+  %34 = getelementptr inbounds %struct.datapartition* null, i32 %33
+  %35 = call i32 undef(%struct.syntaxelement* undef, %struct.img_par* %img, %struct.datapartition* %34)
+  br i1 false, label %.loopexit, label %36
+
+; <label>:36                                      ; preds = %31
+  %37 = load i32* undef, align 4
+  %38 = add i32 %coef_ctr.29, 1
+  %39 = add i32 %38, %37
+  %40 = getelementptr inbounds [2 x i8]* %7, i32 %39, i32 0
+  %41 = load i8* %40, align 1
+  %42 = zext i8 %41 to i32
+  %43 = add nsw i32 %42, %11
+  %44 = getelementptr inbounds %struct.img_par* %img, i32 0, i32 27, i32 undef, i32 %43
+  store i32 0, i32* %44, align 4
+  %45 = add nsw i32 %k.110, 1
+  %46 = icmp slt i32 %45, 65
+  br i1 %46, label %.preheader, label %.loopexit
+
+.loopexit:                                        ; preds = %36, %31, %21, %15, %8
+  ret void
+}