[llvm-branch-commits] [llvm] GlobalISel: Improve extended LLT deduction for G_MERGE_VALUE widenScalar (PR #196399)

[Petar Avramovic via llvm-branch-commits]

https://github.com/petar-avramovic updated https://github.com/llvm/llvm-project/pull/196399

>From f8b583f47016dba5323c39509b5239358548c81d Mon Sep 17 00:00:00 2001
From: Petar Avramovic <Petar.Avramovic at amd.com>
Date: Thu, 7 May 2026 20:57:55 +0200
Subject: [PATCH] GlobalISel: Improve extended LLT deduction for G_MERGE_VALUE
 widenScalar

---
 llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp           | 4 ++--
 llvm/test/CodeGen/AArch64/GlobalISel/legalize-saddsat.mir | 3 +--
 llvm/test/CodeGen/AArch64/GlobalISel/legalize-ssubsat.mir | 3 +--
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 71cda8a480dd7..d705fc29678fc 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2292,11 +2292,11 @@ LegalizerHelper::widenScalarMergeValues(MachineInstr &MI, unsigned TypeIdx,
   // %10:_(s12) = G_MERGE_VALUES %8, %9
 
   const int GCD = std::gcd(SrcSize, WideSize);
-  LLT GCDTy = LLT::scalar(GCD);
+  LLT GCDTy = WideTy.changeElementSize(GCD);
 
   SmallVector<Register, 8> NewMergeRegs;
   SmallVector<Register, 8> Unmerges;
-  LLT WideDstTy = LLT::scalar(NumMerge * WideSize);
+  LLT WideDstTy = WideTy.changeElementSize(NumMerge * WideSize);
 
   // Decompose the original operands if they don't evenly divide.
   for (const MachineOperand &MO : llvm::drop_begin(MI.operands())) {
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-saddsat.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-saddsat.mir
index 608f85088e9a5..a63a5ddbcd590 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-saddsat.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-saddsat.mir
@@ -220,9 +220,8 @@ body:             |
     ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[UADDE]](i32), [[SEXT_INREG2]]
     ; CHECK-NEXT: [[UV4:%[0-9]+]]:_(i8), [[UV5:%[0-9]+]]:_(i8), [[UV6:%[0-9]+]]:_(i8), [[UV7:%[0-9]+]]:_(i8) = G_UNMERGE_VALUES [[UADDE]](i32)
     ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(i8) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[DEF1:%[0-9]+]]:_(s8) = G_IMPLICIT_DEF
     ; CHECK-NEXT: [[MV:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[UV4]](i8), [[UV5]](i8), [[UV6]](i8), [[DEF]](i8)
-    ; CHECK-NEXT: [[MV1:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[DEF1]](s8), [[DEF1]](s8), [[DEF1]](s8), [[DEF1]](s8)
+    ; CHECK-NEXT: [[MV1:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[DEF]](i8), [[DEF]](i8), [[DEF]](i8), [[DEF]](i8)
     ; CHECK-NEXT: [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[MV]](i32), [[MV1]](i32)
     ; CHECK-NEXT: [[SEXT_INREG3:%[0-9]+]]:_(s64) = G_SEXT_INREG [[MV2]], 24
     ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 23
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-ssubsat.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-ssubsat.mir
index f0dad446e3728..19ae38413900b 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-ssubsat.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-ssubsat.mir
@@ -220,9 +220,8 @@ body:             |
     ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[USUBE]](i32), [[SEXT_INREG2]]
     ; CHECK-NEXT: [[UV4:%[0-9]+]]:_(i8), [[UV5:%[0-9]+]]:_(i8), [[UV6:%[0-9]+]]:_(i8), [[UV7:%[0-9]+]]:_(i8) = G_UNMERGE_VALUES [[USUBE]](i32)
     ; CHECK-NEXT: [[DEF:%[0-9]+]]:_(i8) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[DEF1:%[0-9]+]]:_(s8) = G_IMPLICIT_DEF
     ; CHECK-NEXT: [[MV:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[UV4]](i8), [[UV5]](i8), [[UV6]](i8), [[DEF]](i8)
-    ; CHECK-NEXT: [[MV1:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[DEF1]](s8), [[DEF1]](s8), [[DEF1]](s8), [[DEF1]](s8)
+    ; CHECK-NEXT: [[MV1:%[0-9]+]]:_(i32) = G_MERGE_VALUES [[DEF]](i8), [[DEF]](i8), [[DEF]](i8), [[DEF]](i8)
     ; CHECK-NEXT: [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[MV]](i32), [[MV1]](i32)
     ; CHECK-NEXT: [[SEXT_INREG3:%[0-9]+]]:_(s64) = G_SEXT_INREG [[MV2]], 24
     ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 23