[PATCH] Don't report the error when non-dangerous load/store is in branch delay slot

[Sasa Stankovic]

Hi mseaborn,

[mips] Fix a bug - Don't report the error when non-dangerous load/store is in branch delay slot.

http://reviews.llvm.org/D4048

Files:
  lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
  test/MC/Mips/nacl-mask.s

Index: test/MC/Mips/nacl-mask.s
===================================================================
--- test/MC/Mips/nacl-mask.s
+++ test/MC/Mips/nacl-mask.s
@@ -283,3 +283,31 @@
 # CHECK-NEXT:        and     $25, $25, $14
 # CHECK-NEXT:        jalr    $25
 # CHECK-NEXT:        addiu   $4, $zero, 5
+
+
+
+# Test that we can put non-dangerous loads and stores in branch delay slot.
+
+	.align	4
+test6:
+	.set	noreorder
+
+        jal func1
+        sw      $4, 0($sp)
+
+        bal func2
+        lw      $5, 0($t8)
+
+        jalr $t9
+        sw      $sp, 0($sp)
+
+# CHECK-LABEL:   test6:
+
+# CHECK:             jal
+# CHECK-NEXT:        sw      $4, 0($sp)
+
+# CHECK:             bal
+# CHECK-NEXT:        lw      $5, 0($24)
+
+# CHECK:             jalr
+# CHECK-NEXT:        sw      $sp, 0($sp)
Index: lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
@@ -130,27 +130,6 @@
       return;
     }
 
-    // Sandbox loads, stores and SP changes.
-    unsigned AddrIdx;
-    bool IsStore;
-    bool IsMemAccess = isBasePlusOffsetMemoryAccess(Inst.getOpcode(), &AddrIdx,
-                                                    &IsStore);
-    bool IsSPFirstOperand = isStackPointerFirstOperand(Inst);
-    if (IsMemAccess || IsSPFirstOperand) {
-      if (PendingCall)
-        report_fatal_error("Dangerous instruction in branch delay slot!");
-
-      bool MaskBefore = (IsMemAccess
-                         && baseRegNeedsLoadStoreMask(Inst.getOperand(AddrIdx)
-                                                          .getReg()));
-      bool MaskAfter = IsSPFirstOperand && !IsStore;
-      if (MaskBefore || MaskAfter)
-        sandboxLoadStoreStackChange(Inst, AddrIdx, STI, MaskBefore, MaskAfter);
-      else
-        MipsELFStreamer::EmitInstruction(Inst, STI);
-      return;
-    }
-
     // Sandbox calls by aligning call and branch delay to the bundle end.
     // For indirect calls, emit the mask before the call.
     bool IsIndirectCall;
@@ -168,6 +147,27 @@
       PendingCall = true;
       return;
     }
+
+    // Sandbox loads, stores and SP changes.
+    unsigned AddrIdx;
+    bool IsStore;
+    bool IsMemAccess = isBasePlusOffsetMemoryAccess(Inst.getOpcode(), &AddrIdx,
+                                                    &IsStore);
+    bool IsSPFirstOperand = isStackPointerFirstOperand(Inst);
+    if (IsMemAccess || IsSPFirstOperand) {
+      bool MaskBefore = (IsMemAccess
+                         && baseRegNeedsLoadStoreMask(Inst.getOperand(AddrIdx)
+                                                          .getReg()));
+      bool MaskAfter = IsSPFirstOperand && !IsStore;
+      if (MaskBefore || MaskAfter) {
+        if (PendingCall)
+          report_fatal_error("Dangerous instruction in branch delay slot!");
+        sandboxLoadStoreStackChange(Inst, AddrIdx, STI, MaskBefore, MaskAfter);
+        return;
+      }
+      // fallthrough
+    }
+
     if (PendingCall) {
       // Finish the sandboxing sequence by emitting branch delay.
       MipsELFStreamer::EmitInstruction(Inst, STI);
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