[clang] 4467c78 - [clang][RISCV] Set vscale_range attribute based on presence of "v" extension

[Philip Reames via cfe-commits]

Author: Philip Reames
Date: 2022-10-17T11:33:03-07:00
New Revision: 4467c781d7bbf25a3b89a25ccbc0382731f51322

URL: https://github.com/llvm/llvm-project/commit/4467c781d7bbf25a3b89a25ccbc0382731f51322
DIFF: https://github.com/llvm/llvm-project/commit/4467c781d7bbf25a3b89a25ccbc0382731f51322.diff

LOG: [clang][RISCV] Set vscale_range attribute based on presence of "v" extension

This follows the path that AArch64 SVE has taken. Doing this via a function attribute set in the frontend is basically a workaround for the fact that several analyzes which need the information (i.e. known bits, lvi, scev) can't easily use TTI without significant amounts of plumbing changes.

This patch hard codes "v" numbers, and directly follows the SVE precedent as a result. In a follow up, I hope to drive this from RISCVISAInfo.h/cpp instead, but the MinVLen number being returned from that interface seemed to always be 0 (which is wrong), and I haven't figured out what's going wrong there.

Differential Revision: https://reviews.llvm.org/D135894

Added: 
    clang/test/CodeGen/riscv-vector-bits-vscale-range.c

Modified: 
    clang/lib/Basic/Targets/RISCV.cpp
    clang/lib/Basic/Targets/RISCV.h

Removed: 
    


################################################################################
diff  --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index cb0d10abc7e35..b94187f939f27 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -246,6 +246,19 @@ bool RISCVTargetInfo::initFeatureMap(
   return TargetInfo::initFeatureMap(Features, Diags, CPU, ImpliedFeatures);
 }
 
+Optional<std::pair<unsigned, unsigned>>
+RISCVTargetInfo::getVScaleRange(const LangOptions &LangOpts) const {
+  if (LangOpts.VScaleMin || LangOpts.VScaleMax)
+    return std::pair<unsigned, unsigned>(
+        LangOpts.VScaleMin ? LangOpts.VScaleMin : 1, LangOpts.VScaleMax);
+
+  if (hasFeature("v"))
+    // Minimum VLEN=128, Maximum VLEN=64k, and RISCV::RVVBitsPerBlock is 64.
+    return std::pair<unsigned, unsigned>(2, 1024);
+
+  return None;
+}
+
 /// Return true if has this feature, need to sync with handleTargetFeatures.
 bool RISCVTargetInfo::hasFeature(StringRef Feature) const {
   bool Is64Bit = getTriple().getArch() == llvm::Triple::riscv64;

diff  --git a/clang/lib/Basic/Targets/RISCV.h b/clang/lib/Basic/Targets/RISCV.h
index 21c5e7ab795b2..868b1bd5ad041 100644
--- a/clang/lib/Basic/Targets/RISCV.h
+++ b/clang/lib/Basic/Targets/RISCV.h
@@ -90,6 +90,9 @@ class RISCVTargetInfo : public TargetInfo {
                  StringRef CPU,
                  const std::vector<std::string> &FeaturesVec) const override;
 
+  Optional<std::pair<unsigned, unsigned>>
+  getVScaleRange(const LangOptions &LangOpts) const override;
+
   bool hasFeature(StringRef Feature) const override;
 
   bool handleTargetFeatures(std::vector<std::string> &Features,

diff  --git a/clang/test/CodeGen/riscv-vector-bits-vscale-range.c b/clang/test/CodeGen/riscv-vector-bits-vscale-range.c
new file mode 100644
index 0000000000000..067669fa289d2
--- /dev/null
+++ b/clang/test/CodeGen/riscv-vector-bits-vscale-range.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=1 -mvscale-max=1 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=1
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=2 -mvscale-max=2 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=2
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=4 -mvscale-max=4 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=4
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=8 -mvscale-max=8 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=8
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=16 -mvscale-max=16 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=16
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=1 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=1 --check-prefix=CHECK-NOMAX
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=2 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=2 --check-prefix=CHECK-NOMAX
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=4 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=4 --check-prefix=CHECK-NOMAX
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=8 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=8 --check-prefix=CHECK-NOMAX
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=16 -S -emit-llvm -o - %s | FileCheck %s -D#VBITS=16 --check-prefix=CHECK-NOMAX
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -mvscale-min=1 -mvscale-max=0 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-UNBOUNDED
+// RUN: %clang_cc1 -triple riscv64-none-linux-gnu -target-feature +v -S -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-NONE
+
+// CHECK-LABEL: @func() #0
+// CHECK: attributes #0 = { {{.*}} vscale_range([[#VBITS]],[[#VBITS]]) {{.*}} }
+// CHECK-NOMAX: attributes #0 = { {{.*}} vscale_range([[#VBITS]],0) {{.*}} }
+// CHECK-UNBOUNDED: attributes #0 = { {{.*}} vscale_range(1,0) {{.*}} }
+// CHECK-NONE: attributes #0 = { {{.*}} vscale_range(2,1024) {{.*}} }
+void func(void) {}