[PATCH] D141074: [X86] Avoid converting u64 to f32 using x87 on Windows
Craig Topper via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Jan 18 23:14:46 PST 2023
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGa6e3027db7eb: [X86] Avoid converting u64 to f32 using x87 on Windows (authored by icedrocket, committed by craig.topper).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D141074/new/
https://reviews.llvm.org/D141074
Files:
llvm/lib/Target/X86/X86ISelLowering.cpp
llvm/test/CodeGen/X86/uint64-to-float.ll
Index: llvm/test/CodeGen/X86/uint64-to-float.ll
===================================================================
--- llvm/test/CodeGen/X86/uint64-to-float.ll
+++ llvm/test/CodeGen/X86/uint64-to-float.ll
@@ -1,6 +1,8 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=i686-apple-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X86
-; RUN: llc < %s -mtriple=x86_64-apple-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i686-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X86
+; RUN: llc < %s -mtriple=x86_64-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=i686-windows -mattr=+sse2 | FileCheck %s --check-prefix=X86-WIN
+; RUN: llc < %s -mtriple=x86_64-windows -mattr=+sse2 | FileCheck %s --check-prefix=X64-WIN
; Verify that we are using the efficient uitofp --> sitofp lowering illustrated
; by the compiler_rt implementation of __floatundisf.
@@ -42,6 +44,36 @@
; X64-NEXT: cvtsi2ss %rdi, %xmm0
; X64-NEXT: addss %xmm0, %xmm0
; X64-NEXT: retq
+;
+; X86-WIN-LABEL: test:
+; X86-WIN: # %bb.0: # %entry
+; X86-WIN-NEXT: pushl %ebp
+; X86-WIN-NEXT: movl %esp, %ebp
+; X86-WIN-NEXT: andl $-8, %esp
+; X86-WIN-NEXT: subl $8, %esp
+; X86-WIN-NEXT: pushl 12(%ebp)
+; X86-WIN-NEXT: pushl 8(%ebp)
+; X86-WIN-NEXT: calll ___floatundisf
+; X86-WIN-NEXT: addl $8, %esp
+; X86-WIN-NEXT: movl %ebp, %esp
+; X86-WIN-NEXT: popl %ebp
+; X86-WIN-NEXT: retl
+;
+; X64-WIN-LABEL: test:
+; X64-WIN: # %bb.0: # %entry
+; X64-WIN-NEXT: testq %rcx, %rcx
+; X64-WIN-NEXT: js .LBB0_1
+; X64-WIN-NEXT: # %bb.2: # %entry
+; X64-WIN-NEXT: cvtsi2ss %rcx, %xmm0
+; X64-WIN-NEXT: retq
+; X64-WIN-NEXT: .LBB0_1:
+; X64-WIN-NEXT: movq %rcx, %rax
+; X64-WIN-NEXT: shrq %rax
+; X64-WIN-NEXT: andl $1, %ecx
+; X64-WIN-NEXT: orq %rax, %rcx
+; X64-WIN-NEXT: cvtsi2ss %rcx, %xmm0
+; X64-WIN-NEXT: addss %xmm0, %xmm0
+; X64-WIN-NEXT: retq
entry:
%b = uitofp i64 %a to float
ret float %b
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -21898,6 +21898,13 @@
}
assert(SrcVT == MVT::i64 && "Unexpected type in UINT_TO_FP");
+
+ // On Windows, the default precision control on x87 is only 53-bit, and FADD
+ // triggers rounding with that precision, so the final result may be less
+ // accurate. 18014397972611071 is one such case.
+ if (Subtarget.isOSWindows())
+ return SDValue();
+
SDValue ValueToStore = Src;
if (isScalarFPTypeInSSEReg(Op.getValueType()) && !Subtarget.is64Bit()) {
// Bitcasting to f64 here allows us to do a single 64-bit store from
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