[Pipeliner] Correctly update memoperands in the epilog

The pipeliner needs to be conservative when updating the memoperands
of instructions in the epilog. Previously, the pipeliner was changing
the offset of the memoperand based upon the scheduling stage. However,
that is incorrect when control flow branches around the kernel code.
The bug enabled a load and store to the same stack offset to be swapped.

This patch fixes the bug by updating the size of the memoperands to be
UINT_MAX. This conservative value means that dependences will be created
between other loads and stores.

Patch by Brendon Cahoon.

llvm-svn: 328508

diff --git a/llvm/lib/CodeGen/MachinePipeliner.cpp b/llvm/lib/CodeGen/MachinePipeliner.cpp
index 86d2c2e..17c2564 100644 (file)
--- a/llvm/lib/CodeGen/MachinePipeliner.cpp
+++ b/llvm/lib/CodeGen/MachinePipeliner.cpp
@@ -2489,7 +2489,9 @@ void SwingSchedulerDAG::generateEpilog(SMSchedule &Schedule, unsigned LastStage,
           continue;
         MachineInstr *In = &BBI;
         if (Schedule.isScheduledAtStage(getSUnit(In), StageNum)) {
-          MachineInstr *NewMI = cloneInstr(In, EpilogStage - LastStage, 0);
+          // Instructions with memoperands in the epilog are updated with
+          // conservative values.
+          MachineInstr *NewMI = cloneInstr(In, UINT_MAX, 0);
           updateInstruction(NewMI, i == 1, EpilogStage, 0, Schedule, VRMap);
           NewBB->push_back(NewMI);
           InstrMap[NewMI] = In;
@@ -3157,7 +3159,7 @@ void SwingSchedulerDAG::updateMemOperands(MachineInstr &NewMI,
       continue;
     }
     unsigned Delta;
-    if (computeDelta(OldMI, Delta)) {
+    if (Num != UINT_MAX && computeDelta(OldMI, Delta)) {
       int64_t AdjOffset = Delta * Num;
       NewMemRefs[Refs++] =
           MF.getMachineMemOperand(MMO, AdjOffset, MMO->getSize());

diff --git a/llvm/test/CodeGen/Hexagon/swp-memrefs-epilog.ll b/llvm/test/CodeGen/Hexagon/swp-memrefs-epilog.ll
new file mode 100644 (file)
index 0000000..ee01711
--- /dev/null
+++ b/llvm/test/CodeGen/Hexagon/swp-memrefs-epilog.ll
@@ -0,0 +1,102 @@
+; RUN: llc -march=hexagon -O2 -fp-contract=fast < %s | FileCheck %s
+
+; Test that the memoperands for instructions in the epilog are updated
+; correctly. Previously, the pipeliner updated the offset for the memoperands
+; in the epilog. But, the value of the offset is incorrect when control flow
+; branches around the kernel.
+
+; In this test, we check that a load and store to the same location are not
+; swapped due to a bad offset in the memoperands. The store and load are both
+; to r29+32. If the memoperands are updated incorrectly, these are swapped.
+
+; CHECK: [[REG0:r([0-9]+)]] = add(r29,#24)
+; CHECK: [[REG1:r([0-9]+)]] = add([[REG0]],#4)
+; CHECK: memw([[REG1]]+#{{[0-9]}}) = r{{[0-9]+}}
+; CHECK: r{{[0-9]+}} = memw(r29+#{{[0-9]+}})
+
+%s.0 = type { %s.1 }
+%s.1 = type { %s.2 }
+%s.2 = type { %s.3 }
+%s.3 = type { [9 x float] }
+%s.4 = type { %s.5 }
+%s.5 = type { %s.6 }
+%s.6 = type { %s.7 }
+%s.7 = type { [3 x float] }
+
+@g0 = external hidden unnamed_addr constant [29 x i8], align 1
+
+define i32 @f0() unnamed_addr {
+b0:
+  %v0 = alloca %s.0, align 4
+  %v1 = alloca %s.4, align 4
+  %v2 = bitcast %s.0* %v0 to i8*
+  call void @llvm.lifetime.start.p0i8(i64 36, i8* %v2)
+  %v3 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0
+  store float 0x3FEFFF7160000000, float* %v3, align 4
+  %v4 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 1
+  store float 0xBF87867F00000000, float* %v4, align 4
+  %v5 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 2
+  store float 0xBF6185CEE0000000, float* %v5, align 4
+  %v6 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 3
+  store float 0x3F8780BAA0000000, float* %v6, align 4
+  %v7 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 4
+  store float 0x3FEFFF5C60000000, float* %v7, align 4
+  %v8 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 5
+  store float 0xBF74717160000000, float* %v8, align 4
+  %v9 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 6
+  store float 0x3F61FF7160000000, float* %v9, align 4
+  %v10 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 7
+  store float 0x3F74573A80000000, float* %v10, align 4
+  %v11 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 8
+  store float 0x3FEFFFE080000000, float* %v11, align 4
+  %v12 = bitcast %s.4* %v1 to i8*
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* %v12)
+  br label %b1
+
+b1:                                               ; preds = %b1, %b0
+  %v13 = phi i32 [ 0, %b0 ], [ %v29, %b1 ]
+  %v14 = mul nuw nsw i32 %v13, 3
+  %v15 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 %v14
+  %v16 = load float, float* %v15, align 4
+  %v17 = fmul float %v16, 0x3FE7B2B120000000
+  %v18 = add nuw nsw i32 %v14, 1
+  %v19 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 %v18
+  %v20 = load float, float* %v19, align 4
+  %v21 = fmul float %v20, 0x3FDA8BC9C0000000
+  %v22 = fsub float %v21, %v17
+  %v23 = add nuw nsw i32 %v14, 2
+  %v24 = getelementptr inbounds %s.0, %s.0* %v0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 %v23
+  %v25 = load float, float* %v24, align 4
+  %v26 = fmul float %v25, 0x40030D6700000000
+  %v27 = fadd float %v22, %v26
+  %v28 = getelementptr inbounds %s.4, %s.4* %v1, i32 0, i32 0, i32 0, i32 0, i32 0, i32 %v13
+  store float %v27, float* %v28, align 4
+  %v29 = add nuw nsw i32 %v13, 1
+  %v30 = icmp eq i32 %v29, 3
+  br i1 %v30, label %b2, label %b1
+
+b2:                                               ; preds = %b1
+  %v31 = getelementptr inbounds %s.4, %s.4* %v1, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0
+  %v32 = load float, float* %v31, align 4
+  %v33 = fpext float %v32 to double
+  %v34 = getelementptr inbounds %s.4, %s.4* %v1, i32 0, i32 0, i32 0, i32 0, i32 0, i32 1
+  %v35 = load float, float* %v34, align 4
+  %v36 = fpext float %v35 to double
+  %v37 = getelementptr inbounds %s.4, %s.4* %v1, i32 0, i32 0, i32 0, i32 0, i32 0, i32 2
+  %v38 = load float, float* %v37, align 4
+  %v39 = fpext float %v38 to double
+  %v40 = tail call i32 (i8*, ...) @f1(i8* getelementptr inbounds ([29 x i8], [29 x i8]* @g0, i32 0, i32 0), double %v33, double %v36, double %v39)
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %v12)
+  call void @llvm.lifetime.end.p0i8(i64 36, i8* nonnull %v2)
+  ret i32 0
+}
+
+declare i32 @f1(i8* nocapture readonly, ...) local_unnamed_addr
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #0
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #0
+
+attributes #0 = { argmemonly nounwind }