[PATCH] D61124: Fix alignment in AArch64InstructionSelector::emitConstantPoolEntry()

[Hans Wennborg via Phabricator via llvm-commits]

hans created this revision.
hans added reviewers: aemerson, t.p.northover.
Herald added subscribers: hiraditya, kristof.beyls, javed.absar.
Herald added a project: LLVM.

The code was using the alignment of a pointer to the constant, not the
alignment of the constant itself.

      

I guess we got away with it so far because the pointer alignment is
fairly high, but we did end up under-aligning <16 x i8> vectors,
which was caught in the Chromium build (crbug.com/953815).

Please take a look.
+Amara who added the code in r354616, and Tim for general AArch64 goodness maybe in a closer timezone.


https://reviews.llvm.org/D61124

Files:
  llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/select-shuffle-vector.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/select-shuffle-vector.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/select-shuffle-vector.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/select-shuffle-vector.mir
@@ -82,7 +82,7 @@
     ; CHECK-LABEL: name: shuffle_v4i32
     ; CHECK: constants:
     ; CHECK: value:           '<16 x i8> <i8 0, i8 1, i8 2, i8 3, i8 4, i8 5, i8 6, i8 7, i8 12, i8 13, i8 14, i8 15, i8 0, i8 1, i8 2, i8 3>'
-    ; CHECK: alignment:       8
+    ; CHECK: alignment:       16
     ; CHECK: isTargetSpecific: false
     ; CHECK: liveins: $q0, $q1
     ; CHECK: [[COPY:%[0-9]+]]:fpr128 = COPY $q0
@@ -117,7 +117,7 @@
     ; CHECK-LABEL: name: shuffle_tbl_v4i32
     ; CHECK: constants:
     ; CHECK: value:           '<16 x i8> <i8 20, i8 21, i8 22, i8 23, i8 28, i8 29, i8 30, i8 31, i8 4, i8 5, i8 6, i8 7, i8 0, i8 1, i8 2, i8 3>'
-    ; CHECK: alignment:       8
+    ; CHECK: alignment:       16
     ; CHECK: isTargetSpecific: false
     ; CHECK: liveins: $q0, $q1
     ; CHECK: [[COPY:%[0-9]+]]:fpr128 = COPY $q0
@@ -153,7 +153,7 @@
     ; CHECK-LABEL: name: shuffle_v2i64
     ; CHECK: constants:
     ; CHECK: value:           '<16 x i8> <i8 0, i8 1, i8 2, i8 3, i8 4, i8 5, i8 6, i8 7, i8 0, i8 1, i8 2, i8 3, i8 4, i8 5, i8 6, i8 7>'
-    ; CHECK: alignment:       8
+    ; CHECK: alignment:       16
     ; CHECK: isTargetSpecific: false
     ; CHECK: liveins: $q0, $q1
     ; CHECK: [[COPY:%[0-9]+]]:fpr128 = COPY $q0
Index: llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -2572,7 +2572,7 @@
 unsigned
 AArch64InstructionSelector::emitConstantPoolEntry(Constant *CPVal,
                                                   MachineFunction &MF) const {
-  Type *CPTy = CPVal->getType()->getPointerTo();
+  Type *CPTy = CPVal->getType();
   unsigned Align = MF.getDataLayout().getPrefTypeAlignment(CPTy);
   if (Align == 0)
     Align = MF.getDataLayout().getTypeAllocSize(CPTy);


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