[X86][GlobalIsel] support fabs for f80

Author: mattarde

llvm/lib/Target/X86/GISel/X86LegalizerInfo.cpp

@@ -466,6 +466,11 @@ X86LegalizerInfo::X86LegalizerInfo(const X86Subtarget &STI,
                (UseX87 && typeInSet(0, {s80})(Query));
       });
 
+  //TODO: f32 and f64 FABS require xmm support
+  getActionDefinitionsBuilder(G_FABS)
+      .legalFor(UseX87, {s8, s80})
+      .lower();
+
   // fp comparison
   getActionDefinitionsBuilder(G_FCMP)
       .legalFor(HasSSE1 || UseX87, {s8, s32})

llvm/test/CodeGen/X86/GlobalISel/fabs-scalar.ll

@@ -0,0 +1,20 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=x86_64-linux-gnu -global-isel -verify-machineinstrs < %s -o - | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=x86_64-linux -mattr=+x87,-sse,-sse2 | FileCheck %s -check-prefixes=X64
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -global-isel -mattr=+x87,-sse,-sse2  | FileCheck %s -check-prefixes=GISEL
+
+define x86_fp80 @test_x86_fp80_abs(x86_fp80 %arg) {
+; X64-LABEL: test_x86_fp80_abs:
+; X64:       # %bb.0:
+; X64-NEXT:    fldt {{[0-9]+}}(%rsp)
+; X64-NEXT:    fabs
+; X64-NEXT:    retq
+;
+; GISEL-LABEL: test_x86_fp80_abs:
+; GISEL:       # %bb.0:
+; GISEL-NEXT:    fldt {{[0-9]+}}(%rsp)
+; GISEL-NEXT:    fabs
+; GISEL-NEXT:    retq
+  %abs = tail call x86_fp80 @llvm.fabs.f80(x86_fp80 %arg)
+  ret x86_fp80 %abs
+}