[llvm] 8cbfc0b - [X86] Respect blockaddress offsets when performing X86 LEA fixups (#71641)

[via llvm-commits]

Author: Maurice Heumann
Date: 2023-11-10T08:12:18+08:00
New Revision: 8cbfc0b29d7e6c3b1066ef1f2ccba10c8980bdcf

URL: https://github.com/llvm/llvm-project/commit/8cbfc0b29d7e6c3b1066ef1f2ccba10c8980bdcf
DIFF: https://github.com/llvm/llvm-project/commit/8cbfc0b29d7e6c3b1066ef1f2ccba10c8980bdcf.diff

LOG: [X86] Respect blockaddress offsets when performing X86 LEA fixups (#71641)

The X86FixupLEAs pass drops blockaddress offsets, when splitting up slow
3-ops LEAs, as can be seen in this example:

https://godbolt.org/z/bEsc3Poje

Before running the pass, the first instruction in bb.0 is a LEA with
ebp, ebx and a blockaddress.
After the transformation, the blockaddress is missing.

The reason this happens is because the 3-ops LEA is being splitup into a
2-ops LEA + an add instruction.
However, as hasLEAOffset does not take blockaddresses into
consideration, the add is not emitted and thus leading to the offset
being dropped.

Taking blockaddresses into consideration fixes this issue and results in
the add instruction being emitted.

This fixes #71667

Added: 
    llvm/test/CodeGen/X86/lea-fixup-blockaddress.mir

Modified: 
    llvm/lib/Target/X86/X86FixupLEAs.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86FixupLEAs.cpp b/llvm/lib/Target/X86/X86FixupLEAs.cpp
index ceafbf177352a87..beeebf42dfe81ab 100644
--- a/llvm/lib/Target/X86/X86FixupLEAs.cpp
+++ b/llvm/lib/Target/X86/X86FixupLEAs.cpp
@@ -341,7 +341,8 @@ static inline bool hasInefficientLEABaseReg(const MachineOperand &Base,
 }
 
 static inline bool hasLEAOffset(const MachineOperand &Offset) {
-  return (Offset.isImm() && Offset.getImm() != 0) || Offset.isGlobal();
+  return (Offset.isImm() && Offset.getImm() != 0) || Offset.isGlobal() ||
+         Offset.isBlockAddress();
 }
 
 static inline unsigned getADDrrFromLEA(unsigned LEAOpcode) {

diff  --git a/llvm/test/CodeGen/X86/lea-fixup-blockaddress.mir b/llvm/test/CodeGen/X86/lea-fixup-blockaddress.mir
new file mode 100644
index 000000000000000..14134e268613bad
--- /dev/null
+++ b/llvm/test/CodeGen/X86/lea-fixup-blockaddress.mir
@@ -0,0 +1,30 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 3
+# RUN: llc -mtriple=i386-unknown-linux-gnu -mattr=slow-3ops-lea -run-pass x86-fixup-LEAs -o -  %s | FileCheck %s
+
+--- |
+  define i32 @square(i32 %0) local_unnamed_addr {
+    %blub = getelementptr i8, ptr blockaddress(@square, %2), i32 %0
+    indirectbr ptr %blub, [label %2]
+
+  2:
+    ret i32 0
+  }
+
+---
+name:            square
+body:             |
+  ; CHECK-LABEL: name: square
+  ; CHECK: bb.0:
+  ; CHECK-NEXT:   renamable $eax = LEA32r renamable $ebx, 1, renamable $ebp, 0, $noreg
+  ; CHECK-NEXT:   $eax = ADD32ri $eax, target-flags(x86-gotoff) blockaddress(@square, %ir-block.1), implicit-def $eflags
+  ; CHECK-NEXT:   JMP32r killed renamable $eax
+  ; CHECK-NEXT: {{  $}}
+  ; CHECK-NEXT: bb.1 (%ir-block.1, ir-block-address-taken %ir-block.1):
+  ; CHECK-NEXT:   RET 0
+  bb.0:
+    renamable $eax = LEA32r renamable $ebp, 1, renamable $ebx, target-flags(x86-gotoff) blockaddress(@square, %ir-block.1), $noreg
+    JMP32r killed renamable $eax
+
+  bb.1 (%ir-block.1, ir-block-address-taken %ir-block.1):
+    RET 0
+...