[GlobalISel][AArch64] Add support for widening G_FCEIL

This adds support for widening G_FCEIL in LegalizerHelper and
AArch64LegalizerInfo. More specifically, it teaches the AArch64 legalizer to
widen G_FCEIL from a 16-bit float to a 32-bit float when the subtarget doesn't
support full FP 16.

This also updates AArch64/f16-instructions.ll to show that we perform the
correct transformation.

llvm-svn: 349927

3 files changed, 40 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 266409dd1fa..274bc4bf695 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -943,6 +943,15 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
     widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_SEXT);
     Observer.changedInstr(MI);
     return Legalized;
+
+  case TargetOpcode::G_FCEIL:
+    if (TypeIdx != 0)
+      return UnableToLegalize;
+    Observer.changingInstr(MI);
+    widenScalarSrc(MI, WideTy, 1, TargetOpcode::G_FPEXT);
+    widenScalarDst(MI, WideTy, 0, TargetOpcode::G_FPTRUNC);
+    Observer.changedInstr(MI);
+    return Legalized;
   }
 }
 
diff --git a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
index f0700ed0807..91b3fe2c7d3 100644
--- a/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64LegalizerInfo.cpp
@@ -97,9 +97,15 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST) {
 
   getActionDefinitionsBuilder({G_FREM, G_FPOW}).libcallFor({s32, s64});
 
-  // TODO: Handle s16.
   getActionDefinitionsBuilder(G_FCEIL)
-      .legalFor({s32, s64, v2s32, v4s32, v2s64});
+      // If we don't have full FP16 support, then widen s16 to s32 if we
+      // encounter it.
+      .widenScalarIf(
+          [=, &ST](const LegalityQuery &Query) {
+            return Query.Types[0] == s16 && !ST.hasFullFP16();
+          },
+          [=](const LegalityQuery &Query) { return std::make_pair(0, s32); })
+      .legalFor({s16, s32, s64, v2s32, v4s32, v2s64});
 
   getActionDefinitionsBuilder(G_INSERT)
       .unsupportedIf([=](const LegalityQuery &Query) {
diff --git a/llvm/test/CodeGen/AArch64/f16-instructions.ll b/llvm/test/CodeGen/AArch64/f16-instructions.ll
index 352a2753903..13e518a865f 100644
--- a/llvm/test/CodeGen/AArch64/f16-instructions.ll
+++ b/llvm/test/CodeGen/AArch64/f16-instructions.ll
@@ -1,6 +1,17 @@
 ; RUN: llc < %s -mtriple aarch64-unknown-unknown -aarch64-neon-syntax=apple -asm-verbose=false -disable-post-ra -disable-fp-elim | FileCheck %s --check-prefix=CHECK-CVT --check-prefix=CHECK-COMMON
 ; RUN: llc < %s -mtriple aarch64-unknown-unknown -mattr=+fullfp16 -aarch64-neon-syntax=apple -asm-verbose=false -disable-post-ra -disable-fp-elim | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-FP16
 
+; RUN: llc < %s -mtriple aarch64-unknown-unknown -aarch64-neon-syntax=apple \
+; RUN: -asm-verbose=false -disable-post-ra -disable-fp-elim -global-isel \
+; RUN: -global-isel-abort=2 -pass-remarks-missed=gisel-* 2>&1 | FileCheck %s \
+; RUN: --check-prefixes=FALLBACK,GISEL-CVT
+
+; RUN: llc < %s -mtriple aarch64-unknown-unknown -mattr=+fullfp16 \
+; RUN: -aarch64-neon-syntax=apple -asm-verbose=false -disable-post-ra \
+; RUN: -disable-fp-elim -global-isel -global-isel-abort=2 \
+; RUN: -pass-remarks-missed=gisel-* 2>&1 | FileCheck %s \
+; RUN: --check-prefixes=FALLBACK-FP16,GISEL-FP16
+
 target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
 
 ; CHECK-CVT-LABEL: test_fadd:
@@ -1071,6 +1082,18 @@ define half @test_floor(half %a) #0 {
 ; CHECK-FP16-NEXT: frintp h0, h0
 ; CHECK-FP16-NEXT: ret
 
+; FALLBACK-NOT: remark:{{.*}}test_ceil
+; FALLBACK-FP16-NOT: remark:{{.*}}test_ceil
+
+; GISEL-CVT-LABEL: test_ceil:
+; GISEL-CVT-NEXT: fcvt [[FLOAT32:s[0-9]+]], h0
+; GISEL-CVT-NEXT: frintp [[INT32:s[0-9]+]], [[FLOAT32]]
+; GISEL-CVT-NEXT: fcvt h0, [[INT32]]
+; GISEL-CVT-NEXT: ret
+
+; GISEL-FP16-LABEL: test_ceil:
+; GISEL-FP16-NEXT: frintp h0, h0
+; GISEL-FP16-NEXT: ret
 define half @test_ceil(half %a) #0 {
   %r = call half @llvm.ceil.f16(half %a)
   ret half %r