[PATCH] Use ".arch_extension" ARM directive to support hwdiv

[Sumanth Gundapaneni]

Hopefully, this addresses everyone's concerns


http://reviews.llvm.org/D7819

Files:
  lib/Target/ARM/ARMAsmPrinter.cpp
  test/CodeGen/ARM/krait-cpu-div-attribute.ll

Index: lib/Target/ARM/ARMAsmPrinter.cpp
===================================================================
--- lib/Target/ARM/ARMAsmPrinter.cpp
+++ lib/Target/ARM/ARMAsmPrinter.cpp
@@ -16,6 +16,7 @@
 #include "ARM.h"
 #include "ARMConstantPoolValue.h"
 #include "ARMFPUName.h"
+#include "ARMArchExtName.h"
 #include "ARMMachineFunctionInfo.h"
 #include "ARMTargetMachine.h"
 #include "ARMTargetObjectFile.h"
@@ -668,9 +669,13 @@
 
   std::string CPUString = STI.getCPUString();
 
-  // FIXME: remove krait check when GNU tools support krait cpu
-  if (CPUString != "generic" && CPUString != "krait")
-    ATS.emitTextAttribute(ARMBuildAttrs::CPU_name, CPUString);
+  if (CPUString != "generic") {
+    // FIXME: remove krait check when GNU tools support krait cpu
+    if (STI.isKrait())
+      ATS.emitTextAttribute(ARMBuildAttrs::CPU_name, "cortex-a9");
+    else
+      ATS.emitTextAttribute(ARMBuildAttrs::CPU_name, CPUString);
+  }
 
   ATS.emitAttribute(ARMBuildAttrs::CPU_arch, getArchForCPU(CPUString, &STI));
 
@@ -699,6 +704,11 @@
                       ARMBuildAttrs::AllowThumb32);
   }
 
+  // We consider krait as a "cortex-a9" + hwdiv CPU
+  // Enable hwdiv through ".arch_extension idiv"
+  if (STI.isKrait() && (STI.hasDivide() || STI.hasDivideInARMMode()))
+    ATS.emitArchExtension(ARM::HWDIV);
+
   if (STI.hasNEON()) {
     /* NEON is not exactly a VFP architecture, but GAS emit one of
      * neon/neon-fp-armv8/neon-vfpv4/vfpv3/vfpv2 for .fpu parameters */
Index: test/CodeGen/ARM/krait-cpu-div-attribute.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/krait-cpu-div-attribute.ll
@@ -0,0 +1,36 @@
+; Tests the genration of ".arch_extension" attribute for hardware
+; division on krait CPU. For now, krait is recognized as "cortex-a9" + hwdiv
+; Also, tests for the hwdiv instruction on krait CPU
+
+; check for arch_extension/cpu directive
+; RUN: llc < %s -mtriple=armv7-linux-gnueabi -mcpu=krait | FileCheck %s --check-prefix=DIV_EXTENSION
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -mcpu=krait | FileCheck %s --check-prefix=DIV_EXTENSION
+; RUN: llc < %s -mtriple=armv7-linux-gnueabi -mcpu=cortex-a9 | FileCheck %s --check-prefix=NODIV_KRAIT
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -mcpu=cortex-a9 | FileCheck %s --check-prefix=NODIV_KRAIT
+; RUN: llc < %s -mcpu=krait -mattr=-hwdiv,-hwdiv-arm | FileCheck %s --check-prefix=NODIV_KRAIT
+
+; check if correct instruction is emitted by integrated assembler
+; RUN: llc < %s -mtriple=armv7-linux-gnueabi -mcpu=krait -filetype=obj | llvm-objdump -mcpu=krait -triple armv7-linux-gnueabi -d - | FileCheck %s --check-prefix=HWDIV
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -mcpu=krait -filetype=obj | llvm-objdump -mcpu=krait -triple thumbv7-linux-gnueabi -d - | FileCheck %s --check-prefix=HWDIV
+
+; arch_extension attribute
+; DIV_EXTENSION:  .cpu cortex-a9
+; DIV_EXTENSION:  .arch_extension idiv
+; NODIV_KRAIT-NOT:  .arch_extension idiv
+; HWDIV: sdiv
+
+define i32 @main() #0 {
+entry:
+  %retval = alloca i32, align 4
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  %c = alloca i32, align 4
+  store i32 0, i32* %retval
+  store volatile i32 100, i32* %b, align 4
+  store volatile i32 32, i32* %c, align 4
+  %0 = load volatile i32* %b, align 4
+  %1 = load volatile i32* %c, align 4
+  %div = sdiv i32 %0, %1
+  store volatile i32 %div, i32* %a, align 4
+  ret i32 0
+}

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