[llvm] 527e453 - [X86] Add HasCLFLUSH pseudo-predicate (Issue #19039)

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2022-12-08T13:51:14Z
New Revision: 527e453a5bf9e1ab1504199c1b71539b34f25f50

URL: https://github.com/llvm/llvm-project/commit/527e453a5bf9e1ab1504199c1b71539b34f25f50
DIFF: https://github.com/llvm/llvm-project/commit/527e453a5bf9e1ab1504199c1b71539b34f25f50.diff

LOG: [X86] Add HasCLFLUSH pseudo-predicate (Issue #19039)

Similar to what we've done for HasMFence - this puts into place a pseudo-predicate for CLFLUSH instructions that separates it from HasSSE2 to make it easier to use CLFLUSH even when SSE/fpmath has been disabled - technically CLFLUSH has its own CPUID bit, so could be available on x86 cores entirely without SSE, but I don't think thats ever happened or likely to happen.

Added: 
    llvm/test/CodeGen/X86/clflush.ll

Modified: 
    llvm/lib/Target/X86/X86InstrInfo.td
    llvm/lib/Target/X86/X86InstrSSE.td
    llvm/lib/Target/X86/X86Subtarget.h

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86InstrInfo.td b/llvm/lib/Target/X86/X86InstrInfo.td
index 4285df09541f6..72a05901c79d7 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.td
+++ b/llvm/lib/Target/X86/X86InstrInfo.td
@@ -981,6 +981,7 @@ def HasPTWRITE   : Predicate<"Subtarget->hasPTWRITE()">;
 def FPStackf32   : Predicate<"!Subtarget->hasSSE1()">;
 def FPStackf64   : Predicate<"!Subtarget->hasSSE2()">;
 def HasSHSTK     : Predicate<"Subtarget->hasSHSTK()">;
+def HasCLFLUSH   : Predicate<"Subtarget->hasCLFLUSH()">;
 def HasCLFLUSHOPT : Predicate<"Subtarget->hasCLFLUSHOPT()">;
 def HasCLWB      : Predicate<"Subtarget->hasCLWB()">;
 def HasWBNOINVD  : Predicate<"Subtarget->hasWBNOINVD()">;

diff  --git a/llvm/lib/Target/X86/X86InstrSSE.td b/llvm/lib/Target/X86/X86InstrSSE.td
index d50bad93c3c96..561ba99db4afb 100644
--- a/llvm/lib/Target/X86/X86InstrSSE.td
+++ b/llvm/lib/Target/X86/X86InstrSSE.td
@@ -3215,7 +3215,7 @@ let SchedRW = [WriteLoad] in {
 // Flush cache
 def CLFLUSH : I<0xAE, MRM7m, (outs), (ins i8mem:$src),
                "clflush\t$src", [(int_x86_sse2_clflush addr:$src)]>,
-               PS, Requires<[HasSSE2]>;
+               PS, Requires<[HasCLFLUSH]>;
 }
 
 let SchedRW = [WriteNop] in {

diff  --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index 00458fd887dd5..c6bf502a18d21 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -261,6 +261,11 @@ class X86Subtarget final : public X86GenSubtargetInfo {
 
   bool isXRaySupported() const override { return is64Bit(); }
 
+  /// Use clflush if we have SSE2 or we're on x86-64 (even if we asked for
+  /// no-sse2). There isn't any reason to disable it if the target processor
+  /// supports it.
+  bool hasCLFLUSH() const { return hasSSE2() || is64Bit(); }
+
   /// Use mfence if we have SSE2 or we're on x86-64 (even if we asked for
   /// no-sse2). There isn't any reason to disable it if the target processor
   /// supports it.

diff  --git a/llvm/test/CodeGen/X86/clflush.ll b/llvm/test/CodeGen/X86/clflush.ll
new file mode 100644
index 0000000000000..2adb9468e393f
--- /dev/null
+++ b/llvm/test/CodeGen/X86/clflush.ll
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=i386-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X86
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=+sse2 | FileCheck %s --check-prefix=X64
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mattr=-sse2 | FileCheck %s --check-prefix=X64
+
+; It doesn't matter if an x86-64 target has specified "no-sse2"; we still can use clflush.
+
+define void @clflush(ptr %p) nounwind {
+; X86-LABEL: clflush:
+; X86:       # %bb.0:
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    clflush (%eax)
+; X86-NEXT:    retl
+;
+; X64-LABEL: clflush:
+; X64:       # %bb.0:
+; X64-NEXT:    clflush (%rdi)
+; X64-NEXT:    retq
+  tail call void @llvm.x86.sse2.clflush(ptr %p)
+  ret void
+}
+declare void @llvm.x86.sse2.clflush(ptr) nounwind