[llvm] [SelectionDAG] Fix load/store legalization for softened x86_fp80 (PR #209991)
Simon Pilgrim via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 27 03:11:29 PDT 2026
https://github.com/RKSimon updated https://github.com/llvm/llvm-project/pull/209991
>From be9b447c5fa8a7ec91d0e0028b74aa5da2935024 Mon Sep 17 00:00:00 2001
From: Shiyas-N <muhammedshiyasn811 at gmail.com>
Date: Thu, 16 Jul 2026 06:38:45 +0000
Subject: [PATCH 1/5] [SelectionDAG] Fix load/store legalization for softened
x86_fp80
When x86_fp80 is softened to a wider integer type, use extending loads
and truncating stores to preserve the original memory width.
---
.../SelectionDAG/LegalizeFloatTypes.cpp | 24 +++++--
.../CodeGen/X86/x86-fp80-load-store-no-x87.ll | 65 +++++++++++++++++++
2 files changed, 85 insertions(+), 4 deletions(-)
create mode 100644 llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 25cc420c42482..0c869e1b23778 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -1016,10 +1016,19 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_LOAD(SDNode *N) {
~(MachineMemOperand::MOInvariant | MachineMemOperand::MODereferenceable);
SDValue NewL;
if (L->getExtensionType() == ISD::NON_EXTLOAD) {
- NewL = DAG.getLoad(L->getAddressingMode(), L->getExtensionType(), NVT, dl,
- L->getChain(), L->getBasePtr(), L->getOffset(),
- L->getPointerInfo(), NVT, L->getBaseAlign(), MMOFlags,
- L->getAAInfo());
+ // If softening widens the integer representation (e.g. x86_fp80 -> i96),
+ // load the original memory width and extend to the softened type.
+ EVT MemVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
+ if (NVT.bitsGT(MemVT))
+ NewL = DAG.getLoad(L->getAddressingMode(), ISD::EXTLOAD, NVT, dl,
+ L->getChain(), L->getBasePtr(), L->getOffset(),
+ L->getPointerInfo(), MemVT, L->getBaseAlign(),
+ MMOFlags, L->getAAInfo());
+ else
+ NewL = DAG.getLoad(L->getAddressingMode(), L->getExtensionType(), NVT, dl,
+ L->getChain(), L->getBasePtr(), L->getOffset(),
+ L->getPointerInfo(), NVT, L->getBaseAlign(), MMOFlags,
+ L->getAAInfo());
// Legalized the chain result - switch anything that used the old chain to
// use the new one.
ReplaceValueWith(SDValue(N, 1), NewL.getValue(1));
@@ -1423,6 +1432,13 @@ SDValue DAGTypeLegalizer::SoftenFloatOp_STORE(SDNode *N, unsigned OpNo) {
else
Val = GetSoftenedFloat(Val);
+ // If softening widens the integer representation (e.g. x86_fp80 -> i96),
+ // truncate the value before storing to preserve the original memory width.
+ EVT MemVT =
+ EVT::getIntegerVT(*DAG.getContext(), ST->getMemoryVT().getSizeInBits());
+ if (Val.getValueType().bitsGT(MemVT))
+ return DAG.getTruncStore(ST->getChain(), dl, Val, ST->getBasePtr(), MemVT,
+ ST->getMemOperand());
return DAG.getStore(ST->getChain(), dl, Val, ST->getBasePtr(),
ST->getMemOperand());
}
diff --git a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
new file mode 100644
index 0000000000000..dd563bdd746f3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -mattr=-x87 | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i686-unknown-linux-gnu -mattr=-x87 | FileCheck %s --check-prefix=X86
+
+; Verify that x86_fp80 load/store legalization handles widened softened types
+; correctly when x87 is disabled.
+define void @test_load_store_f80(ptr %p, ptr %q) #0 {
+; X64-LABEL: test_load_store_f80:
+; X64: # %bb.0:
+; X64-NEXT: movl 8(%rdi), %eax
+; X64-NEXT: movq (%rdi), %rcx
+; X64-NEXT: movq %rcx, (%rsi)
+; X64-NEXT: movw %ax, 8(%rsi)
+; X64-NEXT: retq
+;
+; X86-LABEL: test_load_store_f80:
+; X86: # %bb.0:
+; X86-NEXT: pushl %esi
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT: movl 8(%ecx), %edx
+; X86-NEXT: movl (%ecx), %esi
+; X86-NEXT: movl 4(%ecx), %ecx
+; X86-NEXT: movl %esi, (%eax)
+; X86-NEXT: movl %ecx, 4(%eax)
+; X86-NEXT: movw %dx, 8(%eax)
+; X86-NEXT: popl %esi
+; X86-NEXT: retl
+ %v = load x86_fp80, ptr %p, align 16
+ store x86_fp80 %v, ptr %q, align 16
+ ret void
+}
+
+; Verify that returning a struct containing x86_fp80 values works with
+; x87 disabled.
+define { x86_fp80, x86_fp80 } @test_struct_ret_f80() #0 {
+; X64-LABEL: test_struct_ret_f80:
+; X64: # %bb.0: # %entry
+; X64-NEXT: movq %rdi, %rax
+; X64-NEXT: movl 8, %ecx
+; X64-NEXT: movq 0, %rdx
+; X64-NEXT: movq %rdx, (%rdi)
+; X64-NEXT: movw %cx, 8(%rdi)
+; X64-NEXT: retq
+;
+; X86-LABEL: test_struct_ret_f80:
+; X86: # %bb.0: # %entry
+; X86-NEXT: pushl %esi
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movl 8, %ecx
+; X86-NEXT: movl 0, %edx
+; X86-NEXT: movl 4, %esi
+; X86-NEXT: movl %esi, 4(%eax)
+; X86-NEXT: movl %edx, (%eax)
+; X86-NEXT: movw %cx, 8(%eax)
+; X86-NEXT: popl %esi
+; X86-NEXT: retl $4
+entry:
+ %r.real = load x86_fp80, ptr null, align 16
+ %.fca.0.insert = insertvalue { x86_fp80, x86_fp80 } zeroinitializer, x86_fp80 %r.real, 0
+ %.fca.1.insert = insertvalue { x86_fp80, x86_fp80 } %.fca.0.insert, x86_fp80 undef, 1
+ ret { x86_fp80, x86_fp80 } %.fca.1.insert
+}
+
+attributes #0 = { nounwind "target-features"="-x87" }
>From 1fffd8997f5c9f60bd3cd94a09ffabe59f6d59c9 Mon Sep 17 00:00:00 2001
From: Shiyas-N <muhammedshiyasn811 at gmail.com>
Date: Thu, 16 Jul 2026 07:25:51 +0000
Subject: [PATCH 2/5] Replace depricated undef with poison
---
llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
index dd563bdd746f3..6bd5b69090cf2 100644
--- a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
+++ b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
@@ -58,7 +58,7 @@ define { x86_fp80, x86_fp80 } @test_struct_ret_f80() #0 {
entry:
%r.real = load x86_fp80, ptr null, align 16
%.fca.0.insert = insertvalue { x86_fp80, x86_fp80 } zeroinitializer, x86_fp80 %r.real, 0
- %.fca.1.insert = insertvalue { x86_fp80, x86_fp80 } %.fca.0.insert, x86_fp80 undef, 1
+ %.fca.1.insert = insertvalue { x86_fp80, x86_fp80 } %.fca.0.insert, x86_fp80 poison, 1
ret { x86_fp80, x86_fp80 } %.fca.1.insert
}
>From 8a58d5fcf414c2829afe8b3c8bb2843d682ea4c8 Mon Sep 17 00:00:00 2001
From: Shiyas-N <muhammedshiyasn811 at gmail.com>
Date: Thu, 16 Jul 2026 08:08:15 +0000
Subject: [PATCH 3/5] remove redundant load call,drop -mattr from the test
---
.../SelectionDAG/LegalizeFloatTypes.cpp | 19 +++++++++----------
.../CodeGen/X86/x86-fp80-load-store-no-x87.ll | 4 ++--
2 files changed, 11 insertions(+), 12 deletions(-)
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 0c869e1b23778..94a074bf052f7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -1019,16 +1019,15 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_LOAD(SDNode *N) {
// If softening widens the integer representation (e.g. x86_fp80 -> i96),
// load the original memory width and extend to the softened type.
EVT MemVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
- if (NVT.bitsGT(MemVT))
- NewL = DAG.getLoad(L->getAddressingMode(), ISD::EXTLOAD, NVT, dl,
- L->getChain(), L->getBasePtr(), L->getOffset(),
- L->getPointerInfo(), MemVT, L->getBaseAlign(),
- MMOFlags, L->getAAInfo());
- else
- NewL = DAG.getLoad(L->getAddressingMode(), L->getExtensionType(), NVT, dl,
- L->getChain(), L->getBasePtr(), L->getOffset(),
- L->getPointerInfo(), NVT, L->getBaseAlign(), MMOFlags,
- L->getAAInfo());
+ ISD::LoadExtType ExtType = L->getExtensionType();
+ EVT LoadMemVT = NVT;
+ if (NVT.bitsGT(MemVT)) {
+ ExtType = ISD::EXTLOAD;
+ LoadMemVT = MemVT;
+ }
+ NewL = DAG.getLoad(L->getAddressingMode(), ExtType, NVT, dl, L->getChain(),
+ L->getBasePtr(), L->getOffset(), L->getPointerInfo(),
+ LoadMemVT, L->getBaseAlign(), MMOFlags, L->getAAInfo());
// Legalized the chain result - switch anything that used the old chain to
// use the new one.
ReplaceValueWith(SDValue(N, 1), NewL.getValue(1));
diff --git a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
index 6bd5b69090cf2..21dc22cb31596 100644
--- a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
+++ b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
@@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -mattr=-x87 | FileCheck %s --check-prefix=X64
-; RUN: llc < %s -mtriple=i686-unknown-linux-gnu -mattr=-x87 | FileCheck %s --check-prefix=X86
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i686-unknown-linux-gnu | FileCheck %s --check-prefix=X86
; Verify that x86_fp80 load/store legalization handles widened softened types
; correctly when x87 is disabled.
>From c8901f6f9816b815cb6f8031c7c4cc2fa512e89a Mon Sep 17 00:00:00 2001
From: Shiyas-N <muhammedshiyasn811 at gmail.com>
Date: Wed, 5 Aug 2026 12:40:29 +0000
Subject: [PATCH 4/5] Remove unnecessary label from test file
---
llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
index 21dc22cb31596..e6dc0369928b2 100644
--- a/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
+++ b/llvm/test/CodeGen/X86/x86-fp80-load-store-no-x87.ll
@@ -35,7 +35,7 @@ define void @test_load_store_f80(ptr %p, ptr %q) #0 {
; x87 disabled.
define { x86_fp80, x86_fp80 } @test_struct_ret_f80() #0 {
; X64-LABEL: test_struct_ret_f80:
-; X64: # %bb.0: # %entry
+; X64: # %bb.0:
; X64-NEXT: movq %rdi, %rax
; X64-NEXT: movl 8, %ecx
; X64-NEXT: movq 0, %rdx
@@ -44,7 +44,7 @@ define { x86_fp80, x86_fp80 } @test_struct_ret_f80() #0 {
; X64-NEXT: retq
;
; X86-LABEL: test_struct_ret_f80:
-; X86: # %bb.0: # %entry
+; X86: # %bb.0:
; X86-NEXT: pushl %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl 8, %ecx
@@ -55,7 +55,6 @@ define { x86_fp80, x86_fp80 } @test_struct_ret_f80() #0 {
; X86-NEXT: movw %cx, 8(%eax)
; X86-NEXT: popl %esi
; X86-NEXT: retl $4
-entry:
%r.real = load x86_fp80, ptr null, align 16
%.fca.0.insert = insertvalue { x86_fp80, x86_fp80 } zeroinitializer, x86_fp80 %r.real, 0
%.fca.1.insert = insertvalue { x86_fp80, x86_fp80 } %.fca.0.insert, x86_fp80 poison, 1
>From f4cc264567283115296067b4571876e1eb8a42de Mon Sep 17 00:00:00 2001
From: Shiyas-N <muhammedshiyasn811 at gmail.com>
Date: Thu, 20 Aug 2026 18:36:07 +0000
Subject: [PATCH 5/5] simplified calls to remove redundant checks
---
.../SelectionDAG/LegalizeFloatTypes.cpp | 20 ++++++-------------
1 file changed, 6 insertions(+), 14 deletions(-)
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
index 94a074bf052f7..5ddc4df11122c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
@@ -1019,15 +1019,10 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_LOAD(SDNode *N) {
// If softening widens the integer representation (e.g. x86_fp80 -> i96),
// load the original memory width and extend to the softened type.
EVT MemVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
- ISD::LoadExtType ExtType = L->getExtensionType();
- EVT LoadMemVT = NVT;
- if (NVT.bitsGT(MemVT)) {
- ExtType = ISD::EXTLOAD;
- LoadMemVT = MemVT;
- }
- NewL = DAG.getLoad(L->getAddressingMode(), ExtType, NVT, dl, L->getChain(),
- L->getBasePtr(), L->getOffset(), L->getPointerInfo(),
- LoadMemVT, L->getBaseAlign(), MMOFlags, L->getAAInfo());
+ NewL = DAG.getLoad(L->getAddressingMode(), ISD::EXTLOAD, NVT, dl,
+ L->getChain(), L->getBasePtr(), L->getOffset(),
+ L->getPointerInfo(), MemVT, L->getBaseAlign(), MMOFlags,
+ L->getAAInfo());
// Legalized the chain result - switch anything that used the old chain to
// use the new one.
ReplaceValueWith(SDValue(N, 1), NewL.getValue(1));
@@ -1435,11 +1430,8 @@ SDValue DAGTypeLegalizer::SoftenFloatOp_STORE(SDNode *N, unsigned OpNo) {
// truncate the value before storing to preserve the original memory width.
EVT MemVT =
EVT::getIntegerVT(*DAG.getContext(), ST->getMemoryVT().getSizeInBits());
- if (Val.getValueType().bitsGT(MemVT))
- return DAG.getTruncStore(ST->getChain(), dl, Val, ST->getBasePtr(), MemVT,
- ST->getMemOperand());
- return DAG.getStore(ST->getChain(), dl, Val, ST->getBasePtr(),
- ST->getMemOperand());
+ return DAG.getTruncStore(ST->getChain(), dl, Val, ST->getBasePtr(), MemVT,
+ ST->getMemOperand());
}
SDValue DAGTypeLegalizer::SoftenFloatOp_ATOMIC_STORE(SDNode *N, unsigned OpNo) {
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