[llvm] [clang] [ARM] .fpu equals fpv5-d16 disables floating point MVE which leads to unsupported MVE instructions assembler error for cortex M85/M55. (PR #71545)
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Tue Nov 7 06:59:03 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: None (simpal01)
<details>
<summary>Changes</summary>
The floating-point and MVE features together specify the MVE functionality that is supported on the Cortex-M85 processor. But the FPU extension for the underlying architecture(armv8.1-m.main) is FPV5 which does not include MVE-F.
So either when we explicitly specify -mfpu=fpv5-d16 or Compiler's -S output and `-save-temps=obj` loses MVE feature which leads to assembler error. What happening here is .fpu directive overrides any previously set features by .cpu directive. Since the the corresponding .fpu generated (.fpu fpv5-d16) does not include MVE-F, it overrides those features even though it is supported and set by the .cpu directive. Looks like .fpu is supposed to do this.
In this case, there should be an .arch_extension directive re-enabling the relevant extensions after .fpu if the goal is to keep these extensions enabled. GCC also does the same.
So this patch enables the MVE features by emitting the below arch extension:
.fpu fpv5-d16
.arch_extension mve.fp
---
Full diff: https://github.com/llvm/llvm-project/pull/71545.diff
3 Files Affected:
- (added) clang/test/CodeGen/arm-v8.1m-check-mve.ll (+56)
- (modified) llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp (+3)
- (modified) llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp (+10-6)
``````````diff
diff --git a/clang/test/CodeGen/arm-v8.1m-check-mve.ll b/clang/test/CodeGen/arm-v8.1m-check-mve.ll
new file mode 100644
index 000000000000000..cfcb0223961e31e
--- /dev/null
+++ b/clang/test/CodeGen/arm-v8.1m-check-mve.ll
@@ -0,0 +1,56 @@
+; REQUIRES: arm-registered-target
+; RUN: %clang --target=arm-none-eabi -mcpu=cortex-m85 -mfloat-abi=hard -save-temps=obj -S -o - %s | FileCheck %s
+; RUN: %clang --target=arm-none-eabi -mcpu=cortex-m55 -mfloat-abi=hard -save-temps=obj -S -o - %s | FileCheck %s
+; RUN: %clang --target=arm-none-eabi -mcpu=cortex-m85 -mfloat-abi=hard -O2 -c -mthumb -save-temps=obj %s
+; RUN: %clang --target=arm-none-eabi -mcpu=cortex-m55 -mfloat-abi=hard -O2 -c -mthumb -save-temps=obj %s
+; CHECK: .fpu fpv5-d16
+; CHECK .arch_extension mve.fp
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv8.1m.main-none-unknown-eabihf"
+
+%struct.dummy_t = type { float, float, float, float }
+
+define dso_local signext i8 @foo(ptr noundef %handle) #0 {
+entry:
+ %handle.addr = alloca ptr, align 4
+ store ptr %handle, ptr %handle.addr, align 4
+ %0 = load ptr, ptr %handle.addr, align 4
+ %a = getelementptr inbounds %struct.dummy_t, ptr %0, i32 0, i32 0
+ %1 = load float, ptr %a, align 4
+ %sub = fsub float 0x3F5439DE40000000, %1
+ %2 = load ptr, ptr %handle.addr, align 4
+ %a1 = getelementptr inbounds %struct.dummy_t, ptr %2, i32 0, i32 0
+ %3 = load float, ptr %a1, align 4
+ %4 = call float @llvm.fmuladd.f32(float 0x3F847AE140000000, float %sub, float %3)
+ store float %4, ptr %a1, align 4
+ %5 = load ptr, ptr %handle.addr, align 4
+ %b = getelementptr inbounds %struct.dummy_t, ptr %5, i32 0, i32 1
+ %6 = load float, ptr %b, align 4
+ %sub2 = fsub float 0x3F5439DE40000000, %6
+ %7 = load ptr, ptr %handle.addr, align 4
+ %b3 = getelementptr inbounds %struct.dummy_t, ptr %7, i32 0, i32 1
+ %8 = load float, ptr %b3, align 4
+ %9 = call float @llvm.fmuladd.f32(float 0x3F947AE140000000, float %sub2, float %8)
+ store float %9, ptr %b3, align 4
+ %10 = load ptr, ptr %handle.addr, align 4
+ %c = getelementptr inbounds %struct.dummy_t, ptr %10, i32 0, i32 2
+ %11 = load float, ptr %c, align 4
+ %sub4 = fsub float 0x3F5439DE40000000, %11
+ %12 = load ptr, ptr %handle.addr, align 4
+ %c5 = getelementptr inbounds %struct.dummy_t, ptr %12, i32 0, i32 2
+ %13 = load float, ptr %c5, align 4
+ %14 = call float @llvm.fmuladd.f32(float 0x3F9EB851E0000000, float %sub4, float %13)
+ store float %14, ptr %c5, align 4
+ %15 = load ptr, ptr %handle.addr, align 4
+ %d = getelementptr inbounds %struct.dummy_t, ptr %15, i32 0, i32 3
+ %16 = load float, ptr %d, align 4
+ %sub6 = fsub float 0x3F5439DE40000000, %16
+ %17 = load ptr, ptr %handle.addr, align 4
+ %d7 = getelementptr inbounds %struct.dummy_t, ptr %17, i32 0, i32 3
+ %18 = load float, ptr %d7, align 4
+ %19 = call float @llvm.fmuladd.f32(float 0x3FA47AE140000000, float %sub6, float %18)
+ store float %19, ptr %d7, align 4
+ ret i8 0
+}
+
+declare float @llvm.fmuladd.f32(float, float, float) #1
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 373d5b59bca6640..20b52ebc544a1ed 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -12648,6 +12648,9 @@ bool ARMAsmParser::enableArchExtFeature(StringRef Name, SMLoc &ExtLoc) {
{ARM::AEK_CRYPTO,
{Feature_HasV8Bit},
{ARM::FeatureCrypto, ARM::FeatureNEON, ARM::FeatureFPARMv8}},
+ {(ARM::AEK_DSP | ARM::AEK_SIMD | ARM::AEK_FP),
+ {Feature_HasV8_1MMainlineBit},
+ {ARM::HasMVEFloatOps}},
{ARM::AEK_FP,
{Feature_HasV8Bit},
{ARM::FeatureVFP2_SP, ARM::FeatureFPARMv8}},
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
index b65d1b24e63d39b..e84b597e4382edc 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMTargetStreamer.cpp
@@ -238,14 +238,18 @@ void ARMTargetStreamer::emitTargetAttributes(const MCSubtargetInfo &STI) {
? ARMBuildAttrs::AllowNeonARMv8_1a
: ARMBuildAttrs::AllowNeonARMv8);
} else {
- if (STI.hasFeature(ARM::FeatureFPARMv8_D16_SP))
+ if (STI.hasFeature(ARM::FeatureFPARMv8_D16_SP)) {
// FPv5 and FP-ARMv8 have the same instructions, so are modeled as one
// FPU, but there are two different names for it depending on the CPU.
- emitFPU(STI.hasFeature(ARM::FeatureD32)
- ? ARM::FK_FP_ARMV8
- : (STI.hasFeature(ARM::FeatureFP64) ? ARM::FK_FPV5_D16
- : ARM::FK_FPV5_SP_D16));
- else if (STI.hasFeature(ARM::FeatureVFP4_D16_SP))
+ if (STI.hasFeature(ARM::FeatureD32))
+ emitFPU(ARM::FK_FP_ARMV8);
+ else {
+ emitFPU(STI.hasFeature(ARM::FeatureFP64) ? ARM::FK_FPV5_D16
+ : ARM::FK_FPV5_SP_D16);
+ if (STI.hasFeature(ARM::HasMVEFloatOps))
+ emitArchExtension(ARM::AEK_SIMD | ARM::AEK_DSP | ARM::AEK_FP);
+ }
+ } else if (STI.hasFeature(ARM::FeatureVFP4_D16_SP))
emitFPU(STI.hasFeature(ARM::FeatureD32)
? ARM::FK_VFPV4
: (STI.hasFeature(ARM::FeatureFP64) ? ARM::FK_VFPV4_D16
``````````
</details>
https://github.com/llvm/llvm-project/pull/71545
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