[llvm] [DAGTypeLegalizer] Add missing BR_CC handler for soft-promoted half operands (PR #196214)
Tony Varghese via llvm-commits
llvm-commits at lists.llvm.org
Wed May 6 18:09:07 PDT 2026
https://github.com/tonykuttai created https://github.com/llvm/llvm-project/pull/196214
`SoftPromoteHalfOperand` had no case for `ISD::BR_CC`, causing a crash when a half-typed `fcmp` result fed directly into a conditional branch. All other comparison-related nodes (`SETCC, SELECT_CC`) were already handled. Add `SoftPromoteHalfOp_BR_CC` following the same pattern as `SoftPromoteHalfOp_SELECT_CC`.
Fixes #195562
>From 40b9897cfab3244a67a8ab6b5d751c17ff924728 Mon Sep 17 00:00:00 2001
From: Tony Varghese <tony.varghese at ibm.com>
Date: Wed, 6 May 2026 10:01:23 +0530
Subject: [PATCH] [DAGTypeLegalizer] Add missing BR_CC handler for
soft-promoted half operands
SoftPromoteHalfOperand had no case for ISD::BR_CC, causing a crash
when a half-typed fcmp result fed directly into a conditional branch.
All other comparison-related nodes (SETCC, SELECT_CC) were already
handled. Add SoftPromoteHalfOp_BR_CC following the same pattern as
SoftPromoteHalfOp_SELECT_CC.
Fixes #195562
---
.../SelectionDAG/LegalizeFloatTypes.cpp | 27 +++
llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h | 1 +
.../PowerPC/soft-promote-half-br-cc.ll | 170 ++++++++++++++++++
3 files changed, 198 insertions(+)
create mode 100644 llvm/test/CodeGen/PowerPC/soft-promote-half-br-cc.ll
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 25f4f75eaedea..26a749f91baf0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -3197,6 +3197,9 @@ bool DAGTypeLegalizer::SoftPromoteHalfOperand(SDNode *N, unsigned OpNo) {
case ISD::STRICT_FP_EXTEND:
case ISD::FP_EXTEND: Res = SoftPromoteHalfOp_FP_EXTEND(N); break;
case ISD::SELECT_CC: Res = SoftPromoteHalfOp_SELECT_CC(N, OpNo); break;
+ case ISD::BR_CC:
+ Res = SoftPromoteHalfOp_BR_CC(N);
+ break;
case ISD::SETCC: Res = SoftPromoteHalfOp_SETCC(N); break;
case ISD::STORE: Res = SoftPromoteHalfOp_STORE(N, OpNo); break;
case ISD::ATOMIC_STORE:
@@ -3309,6 +3312,30 @@ SDValue DAGTypeLegalizer::SoftPromoteHalfOp_FP_TO_XINT_SAT(SDNode *N) {
N->getOperand(1));
}
+SDValue DAGTypeLegalizer::SoftPromoteHalfOp_BR_CC(SDNode *N) {
+ // BR_CC: chain(0), condcode(1), LHS(2), RHS(3), dest(4)
+ // The comparison operands (LHS, RHS) are soft-promoted halfs.
+ SDValue Op0 = N->getOperand(2);
+ SDValue Op1 = N->getOperand(3);
+ SDLoc dl(N);
+
+ EVT SVT = Op0.getValueType();
+ EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), SVT);
+
+ // Get the soft-promoted i16 values
+ Op0 = GetSoftPromotedHalf(Op0);
+ Op1 = GetSoftPromotedHalf(Op1);
+
+ // Promote both comparison operands to the larger FP type.
+ auto PromotionOpcode = GetPromotionOpcode(SVT, NVT);
+ Op0 = DAG.getNode(PromotionOpcode, dl, NVT, Op0);
+ Op1 = DAG.getNode(PromotionOpcode, dl, NVT, Op1);
+
+ // Create a new BR_CC node with promoted operands
+ return DAG.getNode(ISD::BR_CC, dl, MVT::Other, N->getOperand(0),
+ N->getOperand(1), Op0, Op1, N->getOperand(4));
+}
+
SDValue DAGTypeLegalizer::SoftPromoteHalfOp_SELECT_CC(SDNode *N,
unsigned OpNo) {
assert(OpNo == 0 && "Can only soften the comparison values");
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
index 89698a2c77123..84d5b454ba28e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
@@ -806,6 +806,7 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
SDValue SoftPromoteHalfOp_FP_TO_XINT_SAT(SDNode *N);
SDValue SoftPromoteHalfOp_SETCC(SDNode *N);
SDValue SoftPromoteHalfOp_SELECT_CC(SDNode *N, unsigned OpNo);
+ SDValue SoftPromoteHalfOp_BR_CC(SDNode *N);
SDValue SoftPromoteHalfOp_STORE(SDNode *N, unsigned OpNo);
SDValue SoftPromoteHalfOp_ATOMIC_STORE(SDNode *N, unsigned OpNo);
SDValue SoftPromoteHalfOp_STACKMAP(SDNode *N, unsigned OpNo);
diff --git a/llvm/test/CodeGen/PowerPC/soft-promote-half-br-cc.ll b/llvm/test/CodeGen/PowerPC/soft-promote-half-br-cc.ll
new file mode 100644
index 0000000000000..ff4e362f4748a
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/soft-promote-half-br-cc.ll
@@ -0,0 +1,170 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN: -mcpu=pwr9 < %s | FileCheck %s --check-prefix=CHECK-P9
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN: -mcpu=pwr8 < %s | FileCheck %s --check-prefix=CHECK-P8
+
+; Basic comparison with branch
+define i32 @test_br_cc_olt(half %a, half %b) {
+; CHECK-P9-LABEL: test_br_cc_olt:
+; CHECK-P9: # %bb.0:
+; CHECK-P9-NEXT: clrlwi 3, 3, 16
+; CHECK-P9-NEXT: clrlwi 4, 4, 16
+; CHECK-P9-NEXT: mtfprwz 0, 4
+; CHECK-P9-NEXT: mtfprwz 1, 3
+; CHECK-P9-NEXT: xscvhpdp 0, 0
+; CHECK-P9-NEXT: xscvhpdp 1, 1
+; CHECK-P9-NEXT: fcmpu 0, 1, 0
+; CHECK-P9-NEXT: bge 0, .LBB0_2
+; CHECK-P9-NEXT: # %bb.1: # %if.then
+; CHECK-P9-NEXT: li 3, 1
+; CHECK-P9-NEXT: blr
+; CHECK-P9-NEXT: .LBB0_2: # %if.else
+; CHECK-P9-NEXT: li 3, 0
+; CHECK-P9-NEXT: blr
+;
+; CHECK-P8-LABEL: test_br_cc_olt:
+; CHECK-P8: # %bb.0:
+; CHECK-P8-NEXT: mflr 0
+; CHECK-P8-NEXT: .cfi_def_cfa_offset 64
+; CHECK-P8-NEXT: .cfi_offset lr, 16
+; CHECK-P8-NEXT: .cfi_offset r30, -24
+; CHECK-P8-NEXT: .cfi_offset f31, -8
+; CHECK-P8-NEXT: std 30, -24(1) # 8-byte Folded Spill
+; CHECK-P8-NEXT: stfd 31, -8(1) # 8-byte Folded Spill
+; CHECK-P8-NEXT: stdu 1, -64(1)
+; CHECK-P8-NEXT: mr 30, 3
+; CHECK-P8-NEXT: clrldi 3, 4, 48
+; CHECK-P8-NEXT: std 0, 80(1)
+; CHECK-P8-NEXT: bl __extendhfsf2
+; CHECK-P8-NEXT: nop
+; CHECK-P8-NEXT: clrldi 3, 30, 48
+; CHECK-P8-NEXT: fmr 31, 1
+; CHECK-P8-NEXT: bl __extendhfsf2
+; CHECK-P8-NEXT: nop
+; CHECK-P8-NEXT: fcmpu 0, 1, 31
+; CHECK-P8-NEXT: bge 0, .LBB0_2
+; CHECK-P8-NEXT: # %bb.1: # %if.then
+; CHECK-P8-NEXT: li 3, 1
+; CHECK-P8-NEXT: b .LBB0_3
+; CHECK-P8-NEXT: .LBB0_2: # %if.else
+; CHECK-P8-NEXT: li 3, 0
+; CHECK-P8-NEXT: .LBB0_3: # %if.then
+; CHECK-P8-NEXT: addi 1, 1, 64
+; CHECK-P8-NEXT: ld 0, 16(1)
+; CHECK-P8-NEXT: lfd 31, -8(1) # 8-byte Folded Reload
+; CHECK-P8-NEXT: ld 30, -24(1) # 8-byte Folded Reload
+; CHECK-P8-NEXT: mtlr 0
+; CHECK-P8-NEXT: blr
+ %cmp = fcmp olt half %a, %b
+ br i1 %cmp, label %if.then, label %if.else
+if.then:
+ ret i32 1
+if.else:
+ ret i32 0
+}
+
+; Test with constant
+define i32 @test_br_cc_constant(half %a) {
+; CHECK-P9-LABEL: test_br_cc_constant:
+; CHECK-P9: # %bb.0:
+; CHECK-P9-NEXT: clrlwi 3, 3, 16
+; CHECK-P9-NEXT: xxlxor 1, 1, 1
+; CHECK-P9-NEXT: mtfprwz 0, 3
+; CHECK-P9-NEXT: xscvhpdp 0, 0
+; CHECK-P9-NEXT: fcmpu 0, 0, 1
+; CHECK-P9-NEXT: ble 0, .LBB1_2
+; CHECK-P9-NEXT: # %bb.1: # %if.then
+; CHECK-P9-NEXT: li 3, 1
+; CHECK-P9-NEXT: blr
+; CHECK-P9-NEXT: .LBB1_2: # %if.else
+; CHECK-P9-NEXT: li 3, 0
+; CHECK-P9-NEXT: blr
+;
+; CHECK-P8-LABEL: test_br_cc_constant:
+; CHECK-P8: # %bb.0:
+; CHECK-P8-NEXT: mflr 0
+; CHECK-P8-NEXT: stdu 1, -32(1)
+; CHECK-P8-NEXT: std 0, 48(1)
+; CHECK-P8-NEXT: .cfi_def_cfa_offset 32
+; CHECK-P8-NEXT: .cfi_offset lr, 16
+; CHECK-P8-NEXT: clrldi 3, 3, 48
+; CHECK-P8-NEXT: bl __extendhfsf2
+; CHECK-P8-NEXT: nop
+; CHECK-P8-NEXT: xxlxor 0, 0, 0
+; CHECK-P8-NEXT: fcmpu 0, 1, 0
+; CHECK-P8-NEXT: ble 0, .LBB1_2
+; CHECK-P8-NEXT: # %bb.1: # %if.then
+; CHECK-P8-NEXT: li 3, 1
+; CHECK-P8-NEXT: b .LBB1_3
+; CHECK-P8-NEXT: .LBB1_2: # %if.else
+; CHECK-P8-NEXT: li 3, 0
+; CHECK-P8-NEXT: .LBB1_3: # %if.then
+; CHECK-P8-NEXT: addi 1, 1, 32
+; CHECK-P8-NEXT: ld 0, 16(1)
+; CHECK-P8-NEXT: mtlr 0
+; CHECK-P8-NEXT: blr
+ %cmp = fcmp ogt half %a, 0xH0000
+ br i1 %cmp, label %if.then, label %if.else
+if.then:
+ ret i32 1
+if.else:
+ ret i32 0
+}
+
+; vector reduction + branch
+define fastcc i16 @test_vector_reduce_br(half %arg) {
+; CHECK-P9-LABEL: test_vector_reduce_br:
+; CHECK-P9: # %bb.0:
+; CHECK-P9-NEXT: clrlwi 3, 3, 16
+; CHECK-P9-NEXT: xxlxor 1, 1, 1
+; CHECK-P9-NEXT: mtfprwz 0, 3
+; CHECK-P9-NEXT: xscvhpdp 0, 0
+; CHECK-P9-NEXT: fcmpu 0, 0, 1
+; CHECK-P9-NEXT: bc 12, 0, .LBB2_3
+; CHECK-P9-NEXT: # %bb.1:
+; CHECK-P9-NEXT: fcmpu 0, 0, 0
+; CHECK-P9-NEXT: bc 12, 3, .LBB2_3
+; CHECK-P9-NEXT: # %bb.2: # %taken
+; CHECK-P9-NEXT: li 3, 0
+; CHECK-P9-NEXT: blr
+; CHECK-P9-NEXT: .LBB2_3: # %not_taken
+; CHECK-P9-NEXT: li 3, 1
+; CHECK-P9-NEXT: blr
+;
+; CHECK-P8-LABEL: test_vector_reduce_br:
+; CHECK-P8: # %bb.0:
+; CHECK-P8-NEXT: mflr 0
+; CHECK-P8-NEXT: stdu 1, -32(1)
+; CHECK-P8-NEXT: std 0, 48(1)
+; CHECK-P8-NEXT: .cfi_def_cfa_offset 32
+; CHECK-P8-NEXT: .cfi_offset lr, 16
+; CHECK-P8-NEXT: clrldi 3, 3, 48
+; CHECK-P8-NEXT: bl __extendhfsf2
+; CHECK-P8-NEXT: nop
+; CHECK-P8-NEXT: xxlxor 0, 0, 0
+; CHECK-P8-NEXT: fcmpu 0, 1, 0
+; CHECK-P8-NEXT: bc 12, 0, .LBB2_3
+; CHECK-P8-NEXT: # %bb.1:
+; CHECK-P8-NEXT: fcmpu 0, 1, 1
+; CHECK-P8-NEXT: bc 12, 3, .LBB2_3
+; CHECK-P8-NEXT: # %bb.2: # %taken
+; CHECK-P8-NEXT: li 3, 0
+; CHECK-P8-NEXT: b .LBB2_4
+; CHECK-P8-NEXT: .LBB2_3: # %not_taken
+; CHECK-P8-NEXT: li 3, 1
+; CHECK-P8-NEXT: .LBB2_4: # %taken
+; CHECK-P8-NEXT: addi 1, 1, 32
+; CHECK-P8-NEXT: ld 0, 16(1)
+; CHECK-P8-NEXT: mtlr 0
+; CHECK-P8-NEXT: blr
+ %reduce = tail call half @llvm.vector.reduce.fmin.v4f16(<4 x half> zeroinitializer)
+ %cmp = fcmp ole half %reduce, %arg
+ br i1 %cmp, label %taken, label %not_taken
+taken:
+ ret i16 0
+not_taken:
+ ret i16 1
+}
+
+declare half @llvm.vector.reduce.fmin.v4f16(<4 x half>)
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