[PATCH] D70794: [GlobalISel] Fix compiler crash lowering G_LOAD in AArch64.

[Daniel Rodríguez Troitiño via Phabricator via llvm-commits]

drodriguez created this revision.
drodriguez added reviewers: qcolombet, aemerson.
Herald added subscribers: llvm-commits, Petar.Avramovic, volkan, hiraditya, kristof.beyls, rovka.
Herald added a project: LLVM.

When lowering G_LOAD in AArch64, a G_ANYEXT could have been inserted,
even if we were loading from a bigger stored and requesting a smaller
size.

The solution is changing the fixed usage of G_ANYEXT to a conditional
usage of TRUNC or G_ANYEXT depending on the size of the source and the
destination. This seems to avoid the crash in the legalizer.

A test case is included.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70794

Files:
  llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/legalize-load-trunc.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/legalize-load-trunc.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/GlobalISel/legalize-load-trunc.mir
@@ -0,0 +1,32 @@
+# RUN: llc -march=aarch64 -run-pass=legalizer %s -o - -verify-machineinstrs | FileCheck %s
+---
+name:            test_load_trunc
+stack:
+  - { id: 0, type: default, offset: 0, size: 2,
+      alignment: 2, stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+      debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body: |
+  bb.0.entry:
+    successors: %bb.2(0x40000000), %bb.3(0x40000000)
+
+    ; CHECK-LABEL: name: test_load_trunc
+    ; CHECK: [[LOAD:%[0-9]+]]:_(s10) = G_LOAD %0(p0) :: (load 2)
+    ; CHECK: [[TRUNC1:%[0-9]+]]:_(s10) = G_TRUNC [[LOAD]](s16)
+    ; CHECK: [[TRUNC2:%[0-9]+]]:_(s1) = G_TRUNC [[LOAD]](s10)
+    %0:_(p0) = G_FRAME_INDEX %stack.0
+    %1:_(s10) = G_LOAD %0(p0) :: (load 2)
+    %2:_(s1) = G_TRUNC %1(s10)
+    G_BRCOND %2(s1), %bb.2
+    G_BR %bb.3
+
+  bb.2:
+    successors: %bb.4(0x80000000)
+
+    G_BR %bb.4
+
+  bb.3:
+    successors: %bb.4(0x80000000)
+
+  bb.4:
+    RET_ReallyLR
+...
Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2109,7 +2109,7 @@
       default:
         llvm_unreachable("Unexpected opcode");
       case TargetOpcode::G_LOAD:
-        MIRBuilder.buildAnyExt(DstReg, TmpReg);
+        MIRBuilder.buildExtOrTrunc(TargetOpcode::G_ANYEXT, DstReg, TmpReg);
         break;
       case TargetOpcode::G_SEXTLOAD:
         MIRBuilder.buildSExt(DstReg, TmpReg);


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