From a6289dec43c7e84385a4b865db7cba66333f90a1 Mon Sep 17 00:00:00 2001
From: Simon Tatham <simon.tatham@arm.com>
Date: Mon, 3 Jun 2019 11:02:53 +0000
Subject: [PATCH] [ARM] Fix recent breakage of -mfpu=none.
The recent change D60691 introduced a bug in clang when handling
option combinations such as `-mcpu=cortex-m4 -mfpu=none`. Those
options together should select Cortex-M4 but disable all use of
hardware FP, but in fact, now hardware FP instructions can still be
generated in that mode.
The reason is because the handling of FPUVersion::NONE disables all
the same feature names it used to, of which the base one is `vfp2`.
But now there are further features below that, like `vfp2d16fp` and
(following D60694) `fpregs`, which also need to be turned off to
disable hardware FP completely.
Added a tiny test which double-checks that compiling a simple FP
function doesn't access the FP registers.
Reviewers: SjoerdMeijer, dmgreen
Reviewed By: dmgreen
Subscribers: lebedev.ri, javed.absar, kristof.beyls, hiraditya, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D62729
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@362380 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Driver/ToolChains/Arch/ARM.cpp | 9 +++++++--
test/CodeGen/arm-mfpu-none.c | 8 ++++++++
test/Driver/arm-mfpu.c | 2 ++
3 files changed, 17 insertions(+), 2 deletions(-)
create mode 100644 test/CodeGen/arm-mfpu-none.c
diff --git a/lib/Driver/ToolChains/Arch/ARM.cpp b/lib/Driver/ToolChains/Arch/ARM.cpp
index 77fad7ed68..e38ce4d583 100644
--- a/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -430,8 +430,8 @@ fp16_fml_fallthrough:
llvm::ARM::getFPUFeatures(llvm::ARM::FK_NONE, Features);
// Disable hardware FP features which have been enabled.
- // FIXME: Disabling vfp2 and neon should be enough as all the other
- // features are dependent on these 2 features in LLVM. However
+ // FIXME: Disabling fpregs should be enough all by itself, since all
+ // the other FP features are dependent on it. However
// there is currently no easy way to test this in clang, so for
// now just be explicit and disable all known dependent features
// as well.
@@ -439,6 +439,11 @@ fp16_fml_fallthrough:
"neon", "crypto", "dotprod", "fp16fml"})
if (std::find(std::begin(Features), std::end(Features), "+" + Feature) != std::end(Features))
Features.push_back(Args.MakeArgString("-" + Feature));
+
+ // Disable the base feature unconditionally, even if it was not
+ // explicitly in the features list (e.g. if we had +vfp3, which
+ // implies it).
+ Features.push_back("-fpregs");
}
// En/disable crc code generation.
diff --git a/test/CodeGen/arm-mfpu-none.c b/test/CodeGen/arm-mfpu-none.c
new file mode 100644
index 0000000000..ae4b07d863
--- /dev/null
+++ b/test/CodeGen/arm-mfpu-none.c
@@ -0,0 +1,8 @@
+// REQUIRES: arm-registered-target
+// RUN: %clang -target arm-none-eabi -mcpu=cortex-m4 -mfpu=none -S -o - %s | FileCheck %s
+
+// CHECK-LABEL: compute
+// CHECK-NOT: {{s[0-9]}}
+float compute(float a, float b) {
+ return (a+b) * (a-b);
+}
diff --git a/test/Driver/arm-mfpu.c b/test/Driver/arm-mfpu.c
index 33cad80bf1..921afa227c 100644
--- a/test/Driver/arm-mfpu.c
+++ b/test/Driver/arm-mfpu.c
@@ -318,6 +318,7 @@
// RUN: | FileCheck --check-prefix=CHECK-NO-FP %s
// CHECK-NO-FP-NOT: "-target-feature" "+soft-float"
// CHECK-NO-FP: "-target-feature" "+soft-float-abi"
+// CHECK-NO-FP: "-target-feature" "-fpregs"
// CHECK-NO-FP: "-target-feature" "-vfp2"
// CHECK-NO-FP: "-target-feature" "-vfp3"
// CHECK-NO-FP: "-target-feature" "-vfp4"
@@ -363,6 +364,7 @@
// CHECK-SOFT-ABI-FP: "-target-feature" "-fp-armv8"
// CHECK-SOFT-ABI-FP: "-target-feature" "-neon"
// CHECK-SOFT-ABI-FP: "-target-feature" "-crypto"
+// CHECK-SOFT-ABI-FP: "-target-feature" "-fpregs"
// RUN: %clang -target arm-linux-androideabi21 %s -### -c 2>&1 \
// RUN: | FileCheck --check-prefix=CHECK-ARM5-ANDROID-FP-DEFAULT %s
--
2.40.0