Issue:

Stack is formed improperly for long structures passed as byval arguments for
EABI mode.

If we took AAPCS reference, we can found the next statements:

A: "If the argument requires double-word alignment (8-byte), the NCRN (Next
Core Register Number) is rounded up to the next even register number." (5.5
Parameter Passing, Stage C, C.3).

B: "The alignment of an aggregate shall be the alignment of its most-aligned
component." (4.3 Composite Types, 4.3.1 Aggregates).

So if we have structure with doubles (9 double fields) and 3 Core unused
registers (r1, r2, r3): caller should use r2 and r3 registers only.
Currently r1,r2,r3 set is used, but it is invalid.

Callee VA routine should also use r2 and r3 regs only. All is ok here. This
behaviour is guessed by rounding up SP address with ADD+BFC operations.

Fix:
Main fix is in ARMTargetLowering::HandleByVal. If we detected AAPCS mode and
8 byte alignment, we waste odd registers then.

P.S.:
I also improved LDRB_POST_IMM regression test. Since ldrb instruction will
not generated by current regression test after this patch. 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166018 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 21 insertions, 12 deletions

diff --git a/lib/CodeGen/CallingConvLower.cpp b/lib/CodeGen/CallingConvLower.cpp
index cdae33c2441..22b91409240 100644
--- a/lib/CodeGen/CallingConvLower.cpp
+++ b/lib/CodeGen/CallingConvLower.cpp
@@ -50,7 +50,7 @@ void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
   if (MinAlign > (int)Align)
     Align = MinAlign;
   MF.getFrameInfo()->ensureMaxAlignment(Align);
-  TM.getTargetLowering()->HandleByVal(this, Size);
+  TM.getTargetLowering()->HandleByVal(this, Size, Align);
   unsigned Offset = AllocateStack(Size, Align);
   addLoc(CCValAssign::getMem(ValNo, ValVT, Offset, LocVT, LocInfo));
 }
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 6ae44eb3537..b2eb5784879 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1656,22 +1656,31 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
 /// and then confiscate the rest of the parameter registers to insure
 /// this.
 void
-ARMTargetLowering::HandleByVal(CCState *State, unsigned &size) const {
+ARMTargetLowering::HandleByVal(
+    CCState *State, unsigned &size, unsigned Align) const {
   unsigned reg = State->AllocateReg(GPRArgRegs, 4);
   assert((State->getCallOrPrologue() == Prologue ||
           State->getCallOrPrologue() == Call) &&
          "unhandled ParmContext");
   if ((!State->isFirstByValRegValid()) &&
       (ARM::R0 <= reg) && (reg <= ARM::R3)) {
-    State->setFirstByValReg(reg);
-    // At a call site, a byval parameter that is split between
-    // registers and memory needs its size truncated here.  In a
-    // function prologue, such byval parameters are reassembled in
-    // memory, and are not truncated.
-    if (State->getCallOrPrologue() == Call) {
-      unsigned excess = 4 * (ARM::R4 - reg);
-      assert(size >= excess && "expected larger existing stack allocation");
-      size -= excess;
+    if (Subtarget->isAAPCS_ABI() && Align > 4) {
+      unsigned AlignInRegs = Align / 4;
+      unsigned Waste = (ARM::R4 - reg) % AlignInRegs;
+      for (unsigned i = 0; i < Waste; ++i)
+        reg = State->AllocateReg(GPRArgRegs, 4);
+    }
+    if (reg != 0) {
+      State->setFirstByValReg(reg);
+      // At a call site, a byval parameter that is split between
+      // registers and memory needs its size truncated here.  In a
+      // function prologue, such byval parameters are reassembled in
+      // memory, and are not truncated.
+      if (State->getCallOrPrologue() == Call) {
+        unsigned excess = 4 * (ARM::R4 - reg);
+        assert(size >= excess && "expected larger existing stack allocation");
+        size -= excess;
+      }
     }
   }
   // Confiscate any remaining parameter registers to preclude their
diff --git a/lib/Target/ARM/ARMISelLowering.h b/lib/Target/ARM/ARMISelLowering.h
index b5020c97108..9acab0b0834 100644
--- a/lib/Target/ARM/ARMISelLowering.h
+++ b/lib/Target/ARM/ARMISelLowering.h
@@ -480,7 +480,7 @@ namespace llvm {
                 SmallVectorImpl<SDValue> &InVals) const;
 
     /// HandleByVal - Target-specific cleanup for ByVal support.
-    virtual void HandleByVal(CCState *, unsigned &) const;
+    virtual void HandleByVal(CCState *, unsigned &, unsigned) const;
 
     /// IsEligibleForTailCallOptimization - Check whether the call is eligible
     /// for tail call optimization. Targets which want to do tail call