[AArch64][GlobalISel] Fix the LegalityPredicate for lowerIf for G_LOAD/G_STORE

[volkan]

Summary

Currently, Legalizer is trying to lower G_LOAD with a vector type
that has more than two elements due to the incorrect LegalityPredicate.

This patch fixes the issue by removing the multiplication by 8
as MemDesc.Size already contains the size in bits.

[dsanders]

LGTM with the test nit

Would you be willing to rename that Size member to SizeInBits to make the value clearer?

test/CodeGen/AArch64/GlobalISel/legalize-load-v4s32.mir

5

Could you include the full instruction (with operands and types) in this check?

[volkan]

Updated the test to include the full instruction.

[volkan]

In D53679#1275296, @dsanders wrote:

LGTM with the test nit

Would you be willing to rename that Size member to SizeInBits to make the value clearer?

Sure, I'll do that.

lib/Target/AArch64/AArch64LegalizerInfo.cpp

getActionDefinitionsBuilder(G_LOAD)
                                  {s32, p0, 16}})
       .clampScalar(0, s8, s64)
       .widenScalarToNextPow2(0)
       // TODO: We could support sum-of-pow2's but the lowering code doesn't know
       //       how to do that yet.
       .unsupportedIfMemSizeNotPow2()
       // Lower any any-extending loads left into G_ANYEXT and G_LOAD
       .lowerIf([=](const LegalityQuery &Query) {
-        return Query.Types[0].getSizeInBits() != Query.MMODescrs[0].Size * 8;
+        return Query.Types[0].getSizeInBits() != Query.MMODescrs[0].Size;
       })
       .clampNumElements(0, v2s32, v2s32);
 
   getActionDefinitionsBuilder(G_STORE)
       .legalForTypesWithMemSize({{s8, p0, 8},
                                  {s16, p0, 16},
                                  {s32, p0, 32},
                                  {s64, p0, 64},
                                  {p0, p0, 64},
                                  {v2s32, p0, 64}})
       .clampScalar(0, s8, s64)
       .widenScalarToNextPow2(0)
       // TODO: We could support sum-of-pow2's but the lowering code doesn't know
       //       how to do that yet.
       .unsupportedIfMemSizeNotPow2()
       .lowerIf([=](const LegalityQuery &Query) {
         return Query.Types[0].isScalar() &&
-               Query.Types[0].getSizeInBits() != Query.MMODescrs[0].Size * 8;
+               Query.Types[0].getSizeInBits() != Query.MMODescrs[0].Size;
       })
       .clampNumElements(0, v2s32, v2s32);
 
   // Constants
   getActionDefinitionsBuilder(G_CONSTANT)
       .legalFor({p0, s32, s64})
       .clampScalar(0, s32, s64)
       .widenScalarToNextPow2(0);

test/CodeGen/AArch64/GlobalISel/legalize-load-v4s32.mir

+# RUN: not llc -march=aarch64 -o - -run-pass=legalizer -debug-only=legalizer 2>&1 %s | FileCheck %s
+# REQUIRES: asserts
+
+# CHECK: Legalize Machine IR for: load_v4s32
+# CHECK-NEXT: G_LOAD
+# CHECK-NOT: Lower
+# CHECK: unable to legalize instruction
+---
+name:            load_v4s32
+legalized:       false
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $x0
+
+    %0:_(p0) = COPY $x0
+    %1:_(<4 x s32>) = G_LOAD %0(p0) :: (load 16, align 4)
+    %2:_(s32), %3:_(s32), %4:_(s32), %5:_(s32) = G_UNMERGE_VALUES %1(<4 x s32>)
+    $w0 = COPY %5(s32)
+
+...