diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -1113,6 +1113,12 @@
   // where it becomes safe again so stop debugifying here.
   DebugifyIsSafe = false;
 
+  // Add a FSDiscriminator pass right before RA, so that we could get
+  // more precise SampleFDO profile for RA.
+  if (EnableFSDiscriminator)
+    addPass(createMIRAddFSDiscriminatorsPass(
+        sampleprof::FSDiscriminatorPass::Pass1));
+
   // Run register allocation and passes that are tightly coupled with it,
   // including phi elimination and scheduling.
   if (getOptimizeRegAlloc())
@@ -1465,6 +1471,9 @@
 
 /// Add standard basic block placement passes.
 void TargetPassConfig::addBlockPlacement() {
+  if (EnableFSDiscriminator)
+    addPass(createMIRAddFSDiscriminatorsPass(
+        sampleprof::FSDiscriminatorPass::Pass2));
   if (addPass(&MachineBlockPlacementID)) {
     // Run a separate pass to collect block placement statistics.
     if (EnableBlockPlacementStats)
diff --git a/llvm/test/CodeGen/X86/fsafdo_test1.ll b/llvm/test/CodeGen/X86/fsafdo_test1.ll
--- a/llvm/test/CodeGen/X86/fsafdo_test1.ll
+++ b/llvm/test/CodeGen/X86/fsafdo_test1.ll
@@ -3,8 +3,8 @@
 ; Check that fs-afdo discriminators are generated.
 ; CHECK: .loc    1 7 3 is_stmt 0 discriminator 2 # foo.c:7:3
 ; Check: .loc    1 9 5 is_stmt 1 discriminator 2 # foo.c:9:5
-; CHECK: .loc    1 9 5 is_stmt 0 discriminator 268435458 # foo.c:9:5
-; CHECK: .loc    1 7 3 is_stmt 1 discriminator 3892314114 # foo.c:7:3
+; CHECK: .loc    1 9 5 is_stmt 0 discriminator 11266 # foo.c:9:5
+; CHECK: .loc    1 7 3 is_stmt 1 discriminator 11266 # foo.c:7:3
 ; Check that variable __llvm_fs_discriminator__ is generated.
 ; CHECK: .type   __llvm_fs_discriminator__,@object # @__llvm_fs_discriminator__
 ; CHECK: .section        .rodata,"a",@progbits
diff --git a/llvm/test/CodeGen/X86/fsafdo_test2.ll b/llvm/test/CodeGen/X86/fsafdo_test2.ll
--- a/llvm/test/CodeGen/X86/fsafdo_test2.ll
+++ b/llvm/test/CodeGen/X86/fsafdo_test2.ll
@@ -38,9 +38,9 @@
 ;;
 ;; Check that fs-afdo discriminators are generated.
 ; CHECK: .loc    1 23 9 is_stmt 0 discriminator 1 # unroll.c:23:9
-; CHECK: .loc    1 23 9 is_stmt 0 discriminator 3892314113 # unroll.c:23:9
-; CHECK: .loc    1 23 9 is_stmt 0 discriminator 2818572289 # unroll.c:23:9
-; CHECK: .loc    1 23 9 is_stmt 0 discriminator 3623878657 # unroll.c:23:9
+; CHECK: .loc    1 23 9 is_stmt 0 discriminator 3585 # unroll.c:23:9
+; CHECK: .loc    1 23 9 is_stmt 0 discriminator 8705 # unroll.c:23:9
+; CHECK: .loc    1 23 9 is_stmt 0 discriminator 4097 # unroll.c:23:9
 ;;
 ;; Check that variable __llvm_fs_discriminator__ is generated.
 ; CHECK: .type   __llvm_fs_discriminator__,@object # @__llvm_fs_discriminator__