diff --git a/coregrind/Makefile.am b/coregrind/Makefile.am
index 700751dea..48ddd01e9 100644
--- a/coregrind/Makefile.am
+++ b/coregrind/Makefile.am
@@ -363,6 +363,7 @@ COREGRIND_SOURCES_COMMON = \
 	m_debuginfo/d3basics.c \
 	m_debuginfo/debuginfo.c \
 	m_debuginfo/image.c \
+	m_debuginfo/inltab_lookup.c \
 	m_debuginfo/minilzo-inl.c \
 	m_debuginfo/readdwarf.c \
 	m_debuginfo/readdwarf3.c \
diff --git a/coregrind/m_debuginfo/debuginfo.c b/coregrind/m_debuginfo/debuginfo.c
index fb3674565..c801fc5c0 100644
--- a/coregrind/m_debuginfo/debuginfo.c
+++ b/coregrind/m_debuginfo/debuginfo.c
@@ -56,6 +56,7 @@
 #include "priv_d3basics.h"       /* ML_(pp_GX) */
 #include "priv_tytypes.h"
 #include "priv_storage.h"
+#include "priv_inltab_lookup.h"
 #include "priv_readdwarf.h"
 #if defined(VGO_linux) || defined(VGO_solaris) || defined(VGO_freebsd)
 # include "priv_readelf.h"
@@ -345,6 +346,7 @@ static void free_DebugInfo ( DebugInfo* di )
    if (di->loctab)       ML_(dinfo_free)(di->loctab);
    if (di->loctab_fndn_ix) ML_(dinfo_free)(di->loctab_fndn_ix);
    if (di->inltab)       ML_(dinfo_free)(di->inltab);
+   if (di->inltab_lookup) VG_(inltab_lookup_cleanup)(di->inltab_lookup);
    if (di->cfsi_base)    ML_(dinfo_free)(di->cfsi_base);
    if (di->cfsi_m_ix)    ML_(dinfo_free)(di->cfsi_m_ix);
    if (di->cfsi_rd)      ML_(dinfo_free)(di->cfsi_rd);
@@ -2388,13 +2390,12 @@ Bool VG_(get_inline_fnname) ( DiEpoch ep, Addr a, const HChar** inl_fnname )
       return False;
 
    /* Search the inline table for an entry containing this address */
-   /* We search from the end backwards to find the innermost inline function first */
-   for (Word i = si->inltab_used - 1; i >= 0; i--) {
-      if (si->inltab[i].addr_lo <= a && a < si->inltab[i].addr_hi) {
-         /* Found it! Return the inline function name */
-         *inl_fnname = si->inltab[i].inlinedfn;
-         return True;
-      }
+   /* Lookup with hash table cache and binary search fallback */
+   Word inl_idx;
+   if (VG_(inltab_lookup_get)(si->inltab_lookup, a, &inl_idx, si)) {
+      /* Found it! Return the inline function name */
+      *inl_fnname = si->inltab[inl_idx].inlinedfn;
+      return True;
    }
 
    return False;
diff --git a/coregrind/m_debuginfo/inltab_lookup.c b/coregrind/m_debuginfo/inltab_lookup.c
new file mode 100644
index 000000000..89c748415
--- /dev/null
+++ b/coregrind/m_debuginfo/inltab_lookup.c
@@ -0,0 +1,124 @@
+/* VgHashTable-based implementation for inline lookup table.
+   Maps addresses to inline function info indices. */
+
+#include "pub_core_basics.h"
+#include "pub_core_libcbase.h"
+#include "pub_core_libcassert.h"
+#include "pub_core_mallocfree.h"
+#include "pub_core_hashtable.h"
+#include "priv_storage.h"
+
+/* Node structure for VgHashTable
+   Extends VgHashNode with our key (Addr) and value (Word) */
+typedef struct {
+   VgHashNode node;  /* Must be first for VgHashTable API */
+   Word value;       /* The inline table index */
+} InlLookupNode;
+
+/* Binary search for an inline function entry containing address 'a'.
+   Uses the sorted inltab array to efficiently find candidates.
+   Returns the index of the matching entry, or -1 if not found.
+
+   The inltab is sorted by addr_lo, so we:
+   1. Binary search to find entries where addr_lo <= a
+   2. Scan backwards to find an entry that contains address a
+      (this finds the innermost inline function if multiple are nested)
+*/
+static Word binary_search_inltab(const DebugInfo* di, Addr a) {
+   if (di == NULL || di->inltab == NULL || di->inltab_used == 0)
+      return -1;
+
+   Word lo = 0, hi = di->inltab_used;
+
+   /* Binary search: find the first entry where addr_lo > a */
+   while (lo < hi) {
+      Word mid = lo + (hi - lo) / 2;
+      if (a < di->inltab[mid].addr_lo) {
+         hi = mid;
+      } else {
+         lo = mid + 1;
+      }
+   }
+
+   /* lo now points to the first entry where addr_lo > a.
+      Search backwards from lo-1 to find an entry that contains address a */
+   for (Word i = lo - 1; i >= 0; i--) {
+      if (di->inltab[i].addr_lo <= a && a < di->inltab[i].addr_hi) {
+         /* Found it! Return the index */
+         return i;
+      }
+      /* Since we're scanning backwards through sorted addr_lo entries,
+         if we encounter an addr_hi <= a, we can stop as we've passed
+         the potential range */
+      if (di->inltab[i].addr_hi <= a) {
+         break;
+      }
+   }
+
+   return -1;
+}
+
+/* Public API for inline lookup table */
+
+VgHashTable *VG_(inltab_lookup_new)(void) {
+   return VG_(HT_construct)("inltab_lookup");
+}
+
+void VG_(inltab_lookup_insert)(VgHashTable *ht, Addr addr, Word inl_idx) {
+   if (ht == NULL)
+      ht = VG_(inltab_lookup_new)();
+
+   /* Check if entry already exists */
+   InlLookupNode *existing = VG_(HT_lookup)(ht, (UWord)addr);
+   if (existing) {
+      /* Update existing value */
+      existing->value = inl_idx;
+      return;
+   }
+
+   /* Allocate new node */
+   InlLookupNode *node = VG_(malloc)("di.inltab_vghash.node", sizeof(InlLookupNode));
+   if (!node)
+      return;
+   node->node.key = (UWord)addr;
+   node->value = inl_idx;
+
+   VG_(HT_add_node)(ht, node);
+}
+
+/* Enhanced lookup that combines hash table lookup with binary search fallback.
+   First tries the hash table for exact addr_lo matches.
+   If not found, uses binary search on the sorted inltab array.
+   If found via binary search, caches the result in the hash table.
+*/
+Bool VG_(inltab_lookup_get)(VgHashTable *ht, Addr addr, Word *inl_idx,
+                            const DebugInfo* di) {
+   if (ht == NULL)
+      return False;
+
+   /* Try hash table lookup first */
+   InlLookupNode *node = VG_(HT_lookup)(ht, (UWord)addr);
+   if (node) {
+      *inl_idx = node->value;
+      return True;
+   }
+
+   /* Hash table miss, try binary search on the inltab array */
+   Word idx = binary_search_inltab(di, addr);
+   if (idx >= 0) {
+      /* Found via binary search, cache it for future lookups */
+      *inl_idx = idx;
+      VG_(inltab_lookup_insert)(ht, addr, idx);
+      return True;
+   }
+
+   return False;
+}
+
+void VG_(inltab_lookup_cleanup)(VgHashTable *ht) {
+   if (ht == NULL)
+      return;
+
+   /* Free all nodes */
+   VG_(HT_destruct)(ht, VG_(free));
+}
diff --git a/coregrind/m_debuginfo/priv_inltab_lookup.h b/coregrind/m_debuginfo/priv_inltab_lookup.h
new file mode 100644
index 000000000..72785f5bc
--- /dev/null
+++ b/coregrind/m_debuginfo/priv_inltab_lookup.h
@@ -0,0 +1,13 @@
+#ifndef __PRIV_INLTAB_LOOKUP_H
+#define __PRIV_INLTAB_LOOKUP_H
+
+#include "pub_core_basics.h"
+#include "pub_tool_hashtable.h"
+
+extern VgHashTable *VG_(inltab_lookup_new)(void);
+extern void VG_(inltab_lookup_insert)(VgHashTable *ht, Addr addr, Word inl_idx);
+extern Bool VG_(inltab_lookup_get)(VgHashTable *ht, Addr addr, Word *inl_idx,
+                                   const DebugInfo *di);
+extern void VG_(inltab_lookup_cleanup)(VgHashTable *ht);
+
+#endif
\ No newline at end of file
diff --git a/coregrind/m_debuginfo/priv_storage.h b/coregrind/m_debuginfo/priv_storage.h
index 055d75e6f..e7946e931 100644
--- a/coregrind/m_debuginfo/priv_storage.h
+++ b/coregrind/m_debuginfo/priv_storage.h
@@ -44,6 +44,7 @@
 #include "pub_core_basics.h"   // Addr
 #include "pub_core_xarray.h"   // XArray
 #include "pub_core_deduppoolalloc.h" // DedupPoolAlloc
+#include "pub_tool_hashtable.h" // VgHashTable
 #include "priv_d3basics.h"     // GExpr et al.
 #include "priv_image.h"        // DiCursor
 
@@ -953,6 +954,10 @@ struct _DebugInfo {
    UWord   inltab_size;
    SizeT   maxinl_codesz;
 
+   /* Hash table for O(1) inline lookups by address.
+      Maps arbitrary addresses to indices in inltab; populated on-demand during lookups for cache efficiency. */
+   VgHashTable* inltab_lookup;
+
    /* A set of expandable arrays to store CFI summary info records.
       The machine specific information (i.e. the DiCfSI_m struct)
       are stored in cfsi_m_pool, as these are highly duplicated.
diff --git a/coregrind/m_debuginfo/storage.c b/coregrind/m_debuginfo/storage.c
index 12ad68130..477d5ef4e 100644
--- a/coregrind/m_debuginfo/storage.c
+++ b/coregrind/m_debuginfo/storage.c
@@ -51,6 +51,7 @@
 #include "priv_d3basics.h"     /* ML_(pp_GX) */
 #include "priv_tytypes.h"
 #include "priv_storage.h"      /* self */
+#include "priv_inltab_lookup.h"
 
 
 /*------------------------------------------------------------*/
@@ -2164,6 +2165,10 @@ static void canonicaliseInltab ( struct _DebugInfo* di )
 
    /* Free up unused space at the end of the table. */
    shrinkInlTab(di);
+
+   if (di->inltab_lookup == NULL) {
+      di->inltab_lookup = VG_(inltab_lookup_new)();
+   }
 }