[llvm] [update_mir_test_checks] Precommit test for multiple defs of vreg (PR #66483)

[Jay Foad via llvm-commits]

https://github.com/jayfoad created https://github.com/llvm/llvm-project/pull/66483

XFAIL it until it is fixed by an upcoming commit.


>From 8e55421280a283026c43cfba628fc09b9814724a Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Fri, 15 Sep 2023 10:35:01 +0100
Subject: [PATCH 1/2] [update_mir_test_checks] Precommit test for multiple defs
 of vreg

XFAIL it until it is fixed by an upcoming commit.
---
 .../update_mir_test_checks/Inputs/multiple-defs.mir  | 12 ++++++++++++
 .../update_mir_test_checks/multiple-defs.test        |  6 ++++++
 2 files changed, 18 insertions(+)
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_mir_test_checks/Inputs/multiple-defs.mir
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test

diff --git a/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/Inputs/multiple-defs.mir b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/Inputs/multiple-defs.mir
new file mode 100644
index 000000000000000..ff12ed7770beca0
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/Inputs/multiple-defs.mir
@@ -0,0 +1,12 @@
+# RUN: llc -mtriple=x86_64 -run-pass=none -verify-machineinstrs %s -o - | FileCheck %s
+
+---
+name: test
+body: |
+  bb.0:
+    %0:gr32 = IMPLICIT_DEF
+    %1:gr32 = IMPLICIT_DEF
+    %0:gr32 = IMPLICIT_DEF
+    %2:gr32 = IMPLICIT_DEF
+    KILL %0, %2
+...
diff --git a/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test
new file mode 100644
index 000000000000000..7271810535a25f5
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test
@@ -0,0 +1,6 @@
+## Check that update_mir_test_checks handles multiple definitions of the same
+## virtual register (after coming out of SSA form).
+
+# RUN: cp -f %S/Inputs/multiple-defs.mir %t.mir && %update_mir_test_checks %t.mir
+# RUN: FileCheck %t.mir < %t.mir
+# XFAIL: *

>From 5087b5b13dfac1f2c44099e15e6d9d856b5a773a Mon Sep 17 00:00:00 2001
From: Jay Foad <jay.foad at amd.com>
Date: Fri, 15 Sep 2023 10:36:52 +0100
Subject: [PATCH 2/2] [update_mir_test_checks] Handle multiple defs of vreg

When (post-SSA) MIR has multiple defs of the same vreg,
update_mir_test_checks would use different variable names for each def
like this, where DEF and DEF1 both refer to %0:

    %0:gr32 = IMPLICIT_DEF
    %0:gr32 = IMPLICIT_DEF
-->
    ; CHECK: [[DEF:%[0-9]+]]:gr32 = IMPLICIT_DEF
    ; CHECK-NEXT: [[DEF1:%[0-9]+]]:gr32 = IMPLICIT_DEF

This should be harmless, but it messed up the way that mangle_vreg
counts the number of names in vreg_map to come up with a new numeric
suffix, such that you could get the same variable name for different
vregs, like this, where DEF2 refers to both %0 and %2:

    %0:gr32 = IMPLICIT_DEF
    %1:gr32 = IMPLICIT_DEF
    %0:gr32 = IMPLICIT_DEF
    %2:gr32 = IMPLICIT_DEF
-->
    ; CHECK: [[DEF:%[0-9]+]]:gr32 = IMPLICIT_DEF
    ; CHECK-NEXT: [[DEF1:%[0-9]+]]:gr32 = IMPLICIT_DEF
    ; CHECK-NEXT: [[DEF2:%[0-9]+]]:gr32 = IMPLICIT_DEF
    ; CHECK-NEXT: [[DEF2:%[0-9]+]]:gr32 = IMPLICIT_DEF

Fix this by always using the same variable name for the same vreg.
---
 .../update_mir_test_checks/multiple-defs.test              | 1 -
 llvm/utils/update_mir_test_checks.py                       | 7 +++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test
index 7271810535a25f5..1009bcd7571159c 100644
--- a/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test
+++ b/llvm/test/tools/UpdateTestChecks/update_mir_test_checks/multiple-defs.test
@@ -3,4 +3,3 @@
 
 # RUN: cp -f %S/Inputs/multiple-defs.mir %t.mir && %update_mir_test_checks %t.mir
 # RUN: FileCheck %t.mir < %t.mir
-# XFAIL: *
diff --git a/llvm/utils/update_mir_test_checks.py b/llvm/utils/update_mir_test_checks.py
index 815738b23402310..8a539b5fb5ce4bc 100755
--- a/llvm/utils/update_mir_test_checks.py
+++ b/llvm/utils/update_mir_test_checks.py
@@ -204,8 +204,11 @@ def build_function_info_dictionary(
             m = VREG_DEF_RE.match(func_line)
             if m:
                 for vreg in VREG_RE.finditer(m.group("vregs")):
-                    name = mangle_vreg(m.group("opcode"), vreg_map.values())
-                    vreg_map[vreg.group(1)] = name
+                    if vreg.group(1) in vreg_map:
+                        name = vreg_map[vreg.group(1)]
+                    else:
+                        name = mangle_vreg(m.group("opcode"), vreg_map.values())
+                        vreg_map[vreg.group(1)] = name
                     func_line = func_line.replace(
                         vreg.group(1), "[[{}:%[0-9]+]]".format(name), 1
                     )