[x86] Introduce the pconfig instruction

Reviewers: craig.topper, zvi

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D46430

llvm-svn: 331739

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Support/Host.cpp b/llvm/lib/Support/Host.cpp
index ff3a71f2456..d13aa8d5b1a 100644
--- a/llvm/lib/Support/Host.cpp
+++ b/llvm/lib/Support/Host.cpp
@@ -1266,6 +1266,18 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
 
   Features["ibt"] = HasLeaf7 && ((EDX >> 20) & 1);
 
+  // There are two CPUID leafs which information associated with the pconfig
+  // instruction:
+  // EAX=0x7, ECX=0x0 indicates the availability of the instruction (via the 18th
+  // bit of EDX), while the EAX=0x1b leaf returns information on the
+  // availability of specific pconfig leafs.
+  // The target feature here only refers to the the first of these two.
+  // Users might need to check for the availability of specific pconfig
+  // leaves using cpuid, since that information is ignored while
+  // detecting features using the "-march=native" flag.
+  // For more info, see X86 ISA docs.
+  Features["pconfig"] = HasLeaf7 && ((EDX >> 18) & 1);
+
   bool HasLeafD = MaxLevel >= 0xd &&
                   !getX86CpuIDAndInfoEx(0xd, 0x1, &EAX, &EBX, &ECX, &EDX);