[PATCH] D100091: [X86] Fix wrong handle wih "-mno-x87"

[LiuChen via Phabricator via llvm-commits]

LiuChen3 created this revision.
Herald added subscribers: pengfei, hiraditya.
LiuChen3 requested review of this revision.
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When the '-mno-x87' command line option is used, it should prevent all generation
of x87 instructions. Currently there are several circumstances under which it does not.
For example: https://godbolt.org/z/qnPaW7dd6

This patch adds "HasX87" predicates to each X87 instructions and when 80-bit
float pointer is supposed to pass or return on the x87 stack, reporting
an error if X87 is not supported.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100091

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/lib/Target/X86/X86InstrFormats.td
  llvm/lib/Target/X86/X86InstrInfo.td
  llvm/test/CodeGen/X86/nox87-error.ll


Index: llvm/test/CodeGen/X86/nox87-error.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/nox87-error.ll
@@ -0,0 +1,20 @@
+; RUN: not --crash llc < %s -mattr=-x87 -o /dev/null 2>&1 | FileCheck %s --check-prefix NOX87
+; RUN: llc < %s | FileCheck %s
+
+; NOX87: LLVM ERROR: x87 register return with x87 disabled
+
+; CHECK-LABEL: f1:
+; CHECK:       fldt    8(%rsp)
+; CHECK-NEXT:  fstpt   -24(%rsp)
+; CHECK-NEXT:  retq
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local void @f1(x86_fp80 %a) #0 {
+entry:
+  %a.addr = alloca x86_fp80, align 16
+  store x86_fp80 %a, x86_fp80* %a.addr, align 16
+  ret void
+}
+
Index: llvm/lib/Target/X86/X86InstrInfo.td
===================================================================
--- llvm/lib/Target/X86/X86InstrInfo.td
+++ llvm/lib/Target/X86/X86InstrInfo.td
@@ -923,6 +923,7 @@
 def HasVAES      : Predicate<"Subtarget->hasVAES()">;
 def NoVLX_Or_NoVAES : Predicate<"!Subtarget->hasVLX() || !Subtarget->hasVAES()">;
 def HasFXSR      : Predicate<"Subtarget->hasFXSR()">;
+def HasX87       : Predicate<"Subtarget->hasX87()">;
 def HasXSAVE     : Predicate<"Subtarget->hasXSAVE()">;
 def HasXSAVEOPT  : Predicate<"Subtarget->hasXSAVEOPT()">;
 def HasXSAVEC    : Predicate<"Subtarget->hasXSAVEC()">;
Index: llvm/lib/Target/X86/X86InstrFormats.td
===================================================================
--- llvm/lib/Target/X86/X86InstrFormats.td
+++ llvm/lib/Target/X86/X86InstrFormats.td
@@ -458,6 +458,7 @@
 class FPI<bits<8> o, Format F, dag outs, dag ins, string asm>
   : I<o, F, outs, ins, asm, []> {
   let Defs = [FPSW];
+  let Predicates = [HasX87];
 }
 
 // FpI_ - Floating Point Pseudo Instruction template. Not Predicated.
@@ -465,6 +466,7 @@
   : PseudoI<outs, ins, pattern> {
   let FPForm = fp;
   let Defs = [FPSW];
+  let Predicates = [HasX87];
 }
 
 // Templates for instructions that use a 16- or 32-bit segmented address as
Index: llvm/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -2734,6 +2734,10 @@
     // the RET instruction and handled by the FP Stackifier.
     if (VA.getLocReg() == X86::FP0 ||
         VA.getLocReg() == X86::FP1) {
+      // When returning a value via  an X87 register, report an error if X87 is
+      // disabled.
+      if (!Subtarget.hasX87())
+        report_fatal_error("x87 register return with x87 disabled");
       // If this is a copy from an xmm register to ST(0), use an FPExtend to
       // change the value to the FP stack register class.
       if (isScalarFPTypeInSSEReg(VA.getValVT()))
@@ -3070,7 +3074,7 @@
     if ((VA.getLocReg() == X86::FP0 || VA.getLocReg() == X86::FP1) &&
         isScalarFPTypeInSSEReg(VA.getValVT())) {
       if (!Subtarget.hasX87())
-        report_fatal_error("X87 register return with X87 disabled");
+        report_fatal_error("x87 register return with x87 disabled");
       CopyVT = MVT::f80;
       RoundAfterCopy = (CopyVT != VA.getLocVT());
     }
@@ -3241,6 +3245,9 @@
   else
     ValVT = VA.getValVT();
 
+  if (ValVT == MVT::f80 && !Subtarget.hasX87())
+    report_fatal_error("x87 register return with x87 disabled");
+
   // FIXME: For now, all byval parameter objects are marked mutable. This can be
   // changed with more analysis.
   // In case of tail call optimization mark all arguments mutable. Since they


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